Huge sedimentary hiatus in the southern margin of the North China Craton from mid-Mesoproterozoic to Neoproterozoic

ABSTRACT The Meso- to Neoproterozoic Eras were characterized by environmental, evolutionary, and lithospheric stability in the North China Craton (NCC). It is controversial that huge uplift(s) occurred in the North China Craton during this period. The southern NCC developed early terrestrial deposition in the late-Paleoproterozoic and glacial sequence in the late Neoproterozoic record integrated geological history of the NCC in the intervening interval. Geochemistry compositions of mid-Mesoproterozoic carbonaceous slates (ca. 1330 Ma) show similar provenances to the underlying Mesoproterozoic sedimentary rocks in the southern NCC. Detrital zircons from the mid-Mesoproterozoic strata yield U–Pb ages from ca. 2450 to 1850 Ma with minor ages of 2950 and 2750 Ma. U–Pb ages of detrital zircons from the Neoproterozoic strata yield from ca. 1700 to 1000 Ma besides peak ages of 2600, 2400, and 1950 Ma. The early Paleozoic sedimentary rocks also display peak ages between ca. 1850 and 1000 Ma along with peaks at ca. 2500 and 2300 Ma. These detrital zircon ages are quite different from those of the Mesoproterozoic sedimentary rocks in the NCC. According to paleogeography study, the late-Paleoproterozoic to the early Mesoproterozoic clastic sequences are controlled by Xiong’er volcanic event in the southern NCC and carbonate platform developed later. The Mesoproterozoic sequences are overlain disconformably by the Neoproterozoic strata. In combination with compiled magmatic and detrital zircon ages, a sedimentary gap spanned at least 300 Ma from mid-Mesoproterozoic to Neoproterozoic in the southern NCC. Thus, the disconformity between the Mesoproterozoic and Neoproterozoic sedimentary sequences in the southern NCC should represent a huge sedimentary hiatus. Both the variable provenances and huge sedimentary hiatus between the Mesoproterozoic and Neoproterozoic sedimentary sequences support that the NCC might not split from relict landmass of Columbia Supercontinent before Neoproterozoic. The relict landmass was involved in aggregation of the Rodinia supercontinent. Graphic Abstract


Introduction
Cratonic and rift sedimentary assemblages developed in the Paleoproterozoic after the emergence of protocratons are caused by accretions of Archean greenstone terranes (Kroner et al. 1988;Zhao et al. 2004Zhao et al. , 2011Zhai and Santosh 2011;Wang et al. 2020a). The cratons stabilized afterwards and then the earth stepped into 'Middle Age', which was characterized by environmental, evolutionary, and lithospheric stability (Holland 2006;Young 2013;Cawood and Hawkesworth 2014;Zhai and Peng 2020;Brown et al. 2020). Huge sedimentary hiatus (more than 300 Ma) occurred in North American, Australia, Amazon, and Baltica continental blocks, which constituted the core of Rodinia Supercontinent, and led to parallel or lower angle unconformities between Mesoproterozoic and Neoproterozoic strata (Marmont 1987;Dazliel 1997;Torsvik 2003;Jefferson et al. 2007;Li et al. 2008;Davidson 2008;Pirajno et al. 2009;Jarrett et al. 2018). Both Siberia and North China cratons are supposed to be away from the supercontinent (Li et al. 2008(Li et al. , 2019 or the Grenville orogenic belts . Nevertheless, great uplift(s) could last for at least 300 Ma in Siberia (Gladkochub et al. 2010). It is controversial that huge uplift(s) occurred in the North China Craton (NCC) (Qu et al. 2014;Hu et al. 2016;Su 2016;Li et al. :, 2019Zhong et al. 2019;Liu et al. 2020). Whether the huge sedimentary hiatus occurred in the North China Craton (NCC) could be a key to get a better insight of the evolution of the supercontinent.
The southern NCC developed early terrestrial deposits in the Mesoproterozoic and glacial sequence in the late Neoproterozoic record integrated geological history of the NCC in the intervening interval. We provide new detrital zircon ages from the mid-Mesoproterozoic to the early Paleozoic strata and geochemistry of the mid-Mesoproterozoic sedimentary rocks in the southern NCC. With the addition of published detrital zircon ages and geochemistry data, this study presents a huge sedimentary hiatus from mid-Mesoproterozoic to Neoproterozoic in the southern NCC.
Mafic dike swarms (1750 Ma) and anorthositerapakivi granites (ca. 1700 Ma) in the southern NCC have genetic link to the volcanic rocks of the Xiong'er Group . Paleo-to Mesoproterozoic (ca. 1800 to 1500 Ma) alkaline granitoids are interpreted as within-plate granites and could be related to the breakup of Columbia Supercontinent (Lu et al. 2002;Bao et al. 2011;Cui et al. 2013;Deng et al. 2016;Zhao and Deng 2016;Wang et al. 2020b). Neoproterozoic magmatism  in the southern NCC occurred mainly in Lushi-Luanchua area, including trachytes, syenites, and mafic dike swarms and could be related to the break-up of the Rodinia (Liu et al. 2005;Gao et al. 2009;Wang et al. 2011;Hu et al. 2019).
Major, trace, and rare earth elements (REE) of all samples were analyzed. Whole-rock chemical compositions were analyzed at the Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences. Major elements in whole rocks (except FeO and loss on ignition) were determined by standard X-ray fluorescence (XRF) using a Philips Model 1480 spectrometer equipped with a Rh tube. Trace element abundances (Y, Zr, Nb, Hf, Rb, Cs, Ba, Sr, Th, U, V, Cr, Co, Ni, Cu, Sc, and REE) were analyzed by using a combination of emission spectrography (ES) and inductively coupled plasma mass spectrometry (ICP-MS). Detection limits were ≤0.1 wt.% for major elements and ≤2 ppm for most trace elements. The detection limits for Ba, Cr, Rb, Sr, and V are 5 ppm. Correlation coefficients were calculated from the data set composed of the geochemical analyses of all the samples, with the significance level (α) <0.01.
Mineralogical and textural studies of selected samples were carried out using optical microscopy, X-ray diffraction (XRD), and electron probe X-ray microanalysis (EPMA). XRD and EPMA analyses were carried out using at the laboratory of the China University of Geosciences, Beijing (CUGB). The analysis conditions were described by Zuo et al. (2021).
Zircon grains were mounted on adhesive tape, enclosed in a resin mount, and polished to approximately half their thickness with grinding fluid (1 µm). Images of these zircon grains were captured using an optical microscope in transmitted and reflected light. High resolution cathodoluminescence (CL) imaging was performed using a field emission scanning electron microscope (TESCAN, MIRA 3LMH) at the Nanjing Hongchuang Geological Exploration Technology Service Co., Ltd. Both these imaging approaches were utilized to identify internal structures and to select target sites for further U-Pb analysis.  Detrital zircon U-Pb dating of the samples from Neoproterozoic and early Paleozoic strata was accomplished by LA-ICP-MS (Agilent 7900 ICP-MS), with a laser beam (RESOlution M-50-LR Coherent COMPexPro @ 102) repetition rate of 6 Hz and a 26 μm diameter analytical point size, at the State Key Laboratory of Marine Geology (Tongji University). Detailed operating parameters and procedures for the laser ablation system, ICP-MS instrument, and data reduction are as described in Liu et al. (2010). The mid-Mesoproterozoic sample was analyzed at the Wuhan SampleSolution Analytical Technology Co., Ltd., Wuhan, China. Detailed operating conditions for the laser ablation system and the ICP-MS instrument and data reduction are the same as description by Zong et al. (2017). Laser sampling was performed using a GeolasPro laser ablation system that consists of a COMPexPro 102 ArF excimer laser. The spot size and frequency of the laser were set to 32 µm and 5 Hz, respectively, in this study.
Zircon standard 91,500 was used as the external standard and analyzed twice every six or ten analyses. Offline selection and integration of the background and analysis signals, time drift corrections, and quantitative calibration were carried out using the ICPMS DataCal software package for zircon . We use 1500 Ma ( 206 Pb/ 238 U) as the cutoff in selecting 207 Pb/ 206 Pb or 206 Pb/ 238 U ages in the relative age probability diagrams ). All of the uncertainties have been reported at 2 sigma. The assessment of concordant is conducted using the covariance of uncertainties of Ludwig (2003)

Mineralogy and geochemistry of mid-esoproterozoic sedimentary rocks
The XRD results show that carbonaceous slates consist mainly of quartz, illite, and K-feldspar ( Figure S1). Minor apatite, phosphosiderite, illite, and limonite were also observed by EPMA (Figure 4) (Table S1). Illite generally is enriched vanadium in this study and mainly occur as fine flakes or aggregates (Figure 4d) (Table S1). There is no clear boundaries between apatite and quartz ( Figure 4e). Both apatite and phosphosiderite occur as pillared particles and coexist with quartz, denoting an epigenetic origin (Figures 4e and g). Limonite occurs as debris particles and veins in the matrix and crack, and in some case, occurs as colloidal, suggesting occurrence of pyrite.
Analyzed samples for geochemistry study have been reported in Tables S2. All weight percent oxides were recalculated to 100% on a volatile-free and reduced iron basis in Tables S3. Average data of Post-Archean Australian shales (PAAS) (Taylor and McLennan 1985), which are considered as representative of the composition of upper continental crust, are included as a reference. Carbonaceous slates have higher SiO 2 and P 2 O 5 and lower Al 2 O 3 than that of PAAS. There are strong correlations between K 2 O and Al 2 O 3 suggesting occurrence of clays and feldspar, which is also supported by XRD analyses (Figures S1 and S2). Positive correlation between P 2 O 5 and CaO indicates calcium phosphate, such as apatite, rhabdophane or crandallite group ( Figure S2). Since geochemical data are closed or constant-sum data, when one component of a compositional data set increases or decreases in relative abundance, the other components are forced to change as well. Al 2 O 3 is likely to be immobile during weathering, diagenesis, and metamorphism (Cardenas et al. 1996;Bauluz et al., 2000;Meinhold et al. 2007;Qiu et al. 2016). Therefore, the Al 2 O 3 abundances are used as normalization factor to make possible the comparison between different lithologies. If major oxides of analyzed samples are normalized to Al 2 O 3 , the only significant difference in the samples is the SiO 2 /Al 2 O 3 ratio which indicates the variable contents of clay minerals and feldspar (Table S3).
Except Ba and U, all the analyzed samples are depleted in large ion lithophile elements (Rb, Cs, Sr, and Th) ( Figure 5). Rb, Cs, Th, and Sc have significant correlations with Al 2 O 3 and K 2 O ( Figure S2) (Table S4), implying that their distributions are controlled by illitic phases (Bauluz et al., 2000). However, there is no clear correlation between Sr, U, Ba, and other major elements due to their high mobility during chemical weathering. The high field strength elements (HFSEs) (Ta, Zr, Nb, and Hf) are preferentially partionated into melts during crystallization and anatexis, felsic rocks display HFSE enrichment in comparison to mafic rocks (Feng and Kerrich 1990). Carbonaceous slates are enriched in Nb than that of the PAAS (Table S2). HFSEs are also positively correlated with Al 2 O 3 and K 2 O (Table S4).
The distributions of transition trace elements (Ni, Cu, Co, and Cr) are depleted in all samples (Table S2). Ni, Cu, and Co correlate with SiO 2 negatively and with FeO positively (Table S4). V enriched in carbonaceous slates, despite without evident correlation with major elements in this study, can be associated with clay minerals (Breit and Wanty 1991;Tribovillard et al. 2006). Positive correlations among Al 2 O 3 /SiO 2 , CaO, and REE have been observed ( Figures S2). The value of correlation coefficient between REEs and P 2 O 5 is 0.23, which could be caused by the occurrence of phosphosiderite. As element concentrations could be affected by quartz dilution, higher contents of SiO 2 in all rocks analyzed in this study have less REE content than that of PAAS (Table. S2).
Fractionated chondrite-normalized REE patterns, negative Eu anomalies, and LREE fractionated (Figure 6a) suggest that source rocks have undergone near-surface crystal fractionation with feldspar involved.
PAAS-normalized REE patterns show slight enrichment in HREE, but depleted in LREE (Figure 6b). Apatite shows a relatively wide range of chemical variations depending on the environment in which it was formed (Frietsch and Perdahl 1995;Kon et al. 2014). REEs can be released from detrital minerals (apatite and silicate) as REE 3+ ions and adsorbed by secondary phosphate minerals, clay minerals, and Fe-Mn oxides (Köhler et al. 2005;Stille et al. 2009) and therefore apatite has an important role in controlling REE contents and fractionations in the sedimentary rocks. The close affinity of REEs for apatite could account for the slight enrichment in HREE in the samples.

Detrital zircon U-Pb geochronology
CL images show that most grains have preserved magmatic oscillatory zonation. The majority of the zircons also have oscillatory zoning and high Th/U ratios  Figure 7 shows U-Pb concordia age plots and relative age probability diagrams for detrital zircons in this study. Sandstone (21YT-2) and quartzite (BSG0301) were collected in Baishugou Village (Figures 1c and 2). Zircon grains from the sandstone are euhedral to moderate degrees of rounding, mainly colorless, and measures 120-300 μm in size ( Figure S1). Age distributions show dominant populations at 2450, 2050, and 1850 Ma, with two grains at 2950 and 2750 Ma (Figures 7a  and b) (Table S5).
Zircon grains from the quartzite are euhedral to wellrounded, ranging from dark purple to light pink in color, and measures 30-130 μm in size ( Figure S3). Age distributions show two dominant populations between 1700 and 1000 Ma, with subordinate peaks at 2600, 2400, and 1950 Ma (Figures 7c and d) (Tables S6). Carbonaceous phyllite (SCK-4) was collected in Lushi-Luanchun area (Figures 1c and 2). Detrital zircon grains are mainly colorless with moderate degrees of rounding and sphericity ranging from 110 to 220 μm ( Figure S3). Two main populations at 1850 and 1200 Ma with subordinate populations of 2500, 2300, 2100, 1500, and 1000 Ma are shown in Figures 7e and f (Table S7).   Sandstone (17X02) was collected in Mianchi-Queshan area (Figures 1c and 2). Zircon grains are moderate degrees of rounding and sphericity ranging from 90 to 260 μm ( Figure S3) and yield an age distribution with two main populations at 2500 and 1850 Ma with minor populations of 2100 and 1650 Ma (Figures 7g and h) (Table S8).
Siltstone from the Mantou Formation (MD01) was collected from Songshan-Jishan area (Figures 1c and 2). Zircons are moderate degrees of rounding and sphericity with wide ranges from 50 to 200 μm ( Figure S3). Unlike the zircons above, these grains yield an age distribution with two main populations at 1100 and 550 Ma, and subordinate populations of 2600, 2000, 1850, 1300 and 850 Ma (Figures 7i and k) (Table S9). However, there are detrital zircon ages (less than 1000 Ma) with uncertainties (2σ) bigger than 2% of 206 Pb/ 238 U and 207 Pb/ 235 U. These ages should be left out in provenance analysis.

Variable provenances between Meoproterozoic and Nesoproterozoic sequences
Based on the trace elements and REEs distributions, the mid-Meoproterozoic sedimentary rocks show the similar provenances of the underlying early-Mesoproterozoic sandstones and mudrocks (Figures 5 and 6).
Detrital zircon study shows typical cluster ages of 2500 and 1850 Ma (Figure 7), which broadly coincide with amalgamation of micro-continents and finalized cratonization of the NCC, respectively (Zhao et al. 1999;Zhai and Liu 2003;Zhai and Santosh 2011;Zhai and Peng 2020). The NCC underwent Meso-Neoproterozoic extension in its interior, and rifting along its northern, eastern, and southern margin (Zhao 2014;Peng 2015a;Zhang et al. 2017;Li et al. 2019). Alkali granitoids (ca. 1800 to 1500 Ma) and mafic dikes (1360-1200 Ma and 925-800 Ma) occurred in the NCC (Lu et al. 2003;Bao et al. 2011;Peng 2015b;Wang et al. 2016bWang et al. , 2020bZhang et al. 2017). As baddeleyite cannot be retained in sediments during sedimentary cycles, detrital zircon grains aged from mid-Mesoproterozoic to the early-Neoproterozoic may not be derived from weathering of the mafic dikes/sills from the NCC. It is reasonable to infer that these zircon grains would be derived from other continents involved in the Grenville-Sveconorwegian-Sunsas Orogeny. Detrital zircons from the Xinji Formation in this study show no Neoproterozoic aged spectra, which have been identified from contemporaneous strata in other sections (Zuo et al. 2019a(Zuo et al. , 2019b, suggesting limited Neoproterozoic source rocks.

Huge sedimentary hiatus of the southern NCC from mid-Mesoproterozoic to Neoproterozoic
In Songshan-Jishan area, Ma'anshan and Puyu sequences are quite different from the Luotuopan and Hejiazhai sequences in sedimentary facies, and both of them comprise two sedimentary sequences (Zhou 2019;Huang 2020). Detrital zircons from the upper portion of the Ma'anshan Formation yield a dominant peak at ca. 1800 Ma and youngest age at ca. 1655 Ma (Zhang et al. 2016;Meng et al. 2018). In contrast, mid-Mesoproterozoic to Neoproterozoic aged detrital zircon grains were developed in the Hejiazhai and Luotuopan formations (minimum peak at ca. 1000 Ma) (Jia 2018;Huang 2020;Li et al. 2021) (Figure 8). In Mianchi-Queshan area, Neoproterozoic strata disconformably overlies the Paleoproterozoic to early-Mesoproterozoic sedimentary rocks (Su 2016;Zuo et al. 2019b;Pang et al. 2021).
Volcanic tuff from Longjiayuan Formation of the Guandaokou Group in Lushi-Luanchuan area yielded U-Pb ages from 1594 to1541 Ma , which are consistent with the minimum peak age (1511 Ma) of detrital zircons from sandstone above the Fengjiawan sedimentary rocks . Tuffite beds from the Baishugou Formation yielded U-Pb age of ca. 1330 Ma (Figure 2) (Zhu et al. 2020). Therefore, Guandaokou Group could be deposited from ca. 1600 to ca. 1330 Ma. Luanchuan Group can be constrained by ca. 830 Ma gabbro (in the Meiyaogou and Yuku formations) , 840-860 Ma trachyte (in the Dahongkou Formation) (Hu et al. 2019), and minimum peak age of detrital zircons at ca. 1000 Ma from the Sanchuan Formation (Jia 2018;Liu et al. 2019;Li et al. 2020c;this study). A huge sedimentary hiatus (at least 300 Ma), therefore, separates the mid-Mesoproterozoic from the Neoproterozoic deposits in the southern NCC.

Implications for the evolution of the supercontinent
Cratonic and rift sedimentary assemblages developed widely and stabilized proto-cratons from Statherian to Ectasian, which featured the Earth's middle age Zhai and Peng, 2020;Zheng and Zhao 2020;Cawood 2020). Although a number of lower angle unconformities or disconformities occurred in Mesoproterozoic sedimentary successions in the NCC, many of them are distributed locally and can be readily explained by relative sea-level variations (Meng et al. 2011). However, uplift(s) developed in both Yanliao and Zha'ertai-Bayan Obo-Huade basins from mid-Proterozoic to Neoproterozoic (Qu et al. 2010;Hu et al. 2016;Zhong et al. 2019;Liu et al. 2020;Zhang et al. 2020). Mesoproterozoic sedimentary sequences are absent in the Xuhuai Basin (He et al. 2016;Sun et al. 2020). Intense weathering occurred widely in the supercontinent cycle, and general planation can be encouraged by high denudation rate in vegetation-free landscapes (Eriksson et al. 1998;Campbell and Allen 2008). After the earlier, still nearly horizontal unconformity, subsequent unconformities tend to conform to this original cratonic planation surface. Thus, the Mesoproterozoic sequences are disconformably overlain by the Neoproterozoic strata ( Figure 9).
Greenville-aged detrital zircons also occurred in the Neoproterozoic sequences from these areas (Figure 9). Although the NCC might not involved in the Rodinia Supercontinent directly and was located far from the Grenville orogeny (Weil et al. 1998;Torsvik 2003;Li et al. 2008Li et al. , 2019Pisarevsky et al. 2014;Zhai et al. 2015;Cawood et al. 2016), NCC may not split from relict landmass of Columbia Supercontinent, and was connected with continents involved in Grenville-Sveconorwegian-Sunsas Orogeny. Huge uplift (s) likely lead to the long-term hiatus in the NCC.  Jia (2018) and this study. It is noticed the collected data with 1σ uncertainties are multiplied by 2 to get 2σ uncertainties approximately. Synthetic age spectra are designed to represent potential detrital zircon source regions. These are assumed to have a normal distribution with 2σ uncertainties and are plotted in the MDS map using 500 synthetic data points.

Conclusions
Detrital zircon ages in the Neoproterozoic and early Paleozoic sedimentary sequences indicate variable provenances in compared with those from the Mesoproterozoic strata. Geochemistry compositions of mid-Mesoproterozoic carbonaceous slates (ca. 1330 Ma) show similar provenances to the underlying Mesoproterozoic sedimentary rocks in the southern NCC. Distribution and sedimentation of Mesoproterozoic clastic rocks at the southern NCC were controlled by the Xiong'er volcanic event just existed in the Paleoproterozoic to the early-Mesoproterozoic, and then epicontinental sea deposits occurred on the NCC until mid-Mesoproterozoic. Neoproterozoic sedimentary successions overlies the early-Mesoproterozoic strata disconformably. According to the constraints of magmatic and detrital zircon ages, the disconformity should represent a huge sedimentary hiatus, which should be more than 300 Ma. Uplift(s) could occurred widely from the Mesoproterozoic to Neoproterozoic in the NCC and caused the disconformities. We therefore proposed that the NCC might not split from relict landmass of Columbia Supercontinent before Neoproterozoic.

Highlights
1. Variations of sources-changes in detrital zircon age from Mesoproterozoic to Neoproterozoic.
2. Long last sedimentary gap from mid-Mesoproterozoic to Neoproterozoic.
3. The North China Craton might not split from relict landmass of Columbia Supercontinent before Neoproterozoic.