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Hadean Detrital Zircon in the North China Craton

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Hadean Detrital Zircon in the North China Craton Journal of Mineralogical and Petrological Sciences, Volume 111, page 283–291, 2016 Hadean detrital zircon in the North China Craton Zhuang LI*, Bin CHEN** and Chunjing WEI* *The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, PR China **School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China Due to a lack of rock samples from the Hadean Eon, the Hadean zircons have become an important means of understanding the Earth’s earliest history. This study reports the occurrence of a Hadean detrital zircon with a concordia U–Pb age of 4081 ± 71 Ma and 207Pb/206Pb age of 4087 ± 31 Ma from the Paleoproterozoic meta- sedimentary rocks in the Jiao–Liao–Ji Belt (JLJB) in the North China Craton. The analyzed zircon grain exhibits low luminescence and striped absorption and has relatively high Th/U ratio (0.37), all suggesting an igneous origin. It is euhedral with length/width ratios of 3:2, implying a short distance of transportation from its source. The Hadean age is ~ 570 million years older than the oldest zircon previously identified in the JLJB. This further demonstrates the existence of a Hadean continental crustal remnant in the North China Craton. In addition, to our knowledge, it is the first case of a Hadean zircon being recognized in the Paleoproterozoic sediments on Earth. The documentation of a 4.09 Ga detrital zircon not only provides a geochronological record of the oldest known crustal materials in the JLJB, but also identifies the geological environment for further exploration for the Hadean zircons or even the Hadean rocks. Keywords: Hadean zircon, U–Pb age, Paleoproterozoic metasedimentary, Jiao–Liao–Ji Belt, North China Craton INTRODUCTION Narryer and Jack Hills (and adjacent granitoids) of the Narryer Terrane in Western Australia (e.g., Compston The Hadean zircons and rocks are keys to deciphering the and Pidgeon, 1986; Wilde et al., 2001; Wyche et al., evolution of crustal rocks formed during the Pre–archean 2004; Cavosie et al., 2007; Harrison, 2009; Nebel et Eon (Chaotian (>4.5 Ga) and Hadean (4.0–4.5 Ga)) (Rud- al., 2014; Valley et al., 2014). Hadean zircon occurrences nick and Gao, 2003; Goldblatt et al., 2010; Moyen, 2011; outside Western Australia have been also reported in Nebel et al., 2014), making possible new avenues for Canada (Iizuka et al., 2006, 2009), west Greenland early Earth research. However, the Hadean rocks on (Mojzsis and Harrison, 2002), and China (Fig. 1a and Earth are only identified in Canada as the 3.94–4.03 Ga Table 1; Duo et al., 2007a, 2007b; Wang et al., 2007; magmatic protoliths of the Acasta gneisses in the Wop- Diwu et al., 2010; Cui et al., 2013; Xing et al., 2014). may Orogenic Belt (e.g., Iizuka et al., 2006, 2007, 2009). For the first time, we report the occurrence of a 4.09 Ga Comparatively, the Hadean zircons have attracted consid- zircon in the Paleoproterozoic metasedimentary rocks in erably more attention, as they are widespread and exhibit the Jiao–Liao–Ji Belt (JLJB) in the North China Craton robust chemical and physical features that make them (NCC). The U–Pb isotopic dating using the laser abla- survive extreme conditions (Nebel et al., 2014; Xing et tion–inductively coupled plasma–mass spectrometer (LA– al., 2014), thereby providing a means of understanding ICP–MS) method reveals that the 4.09 Ga zircon is a de- the evolution of the early Earth. trital zircon within the 2.0–1.9 Ga staurolite–garnet–mica It should be noted that most of the detrital or the schist. This study will deepen our understanding of the xenocrystic zircons older than 4.0 Ga are found at Mt. developmental history of early Earth and suggest areas for the exploration of the Hadean zircons or even the doi:10.2465/jmps.150929 Hadean rocks. Z. Li, [email protected] Corresponding author 284 Z. Li, B. Chen and C. Wei Figure 1. The distribution of the Hadean zircons. (a) Geological sketch of China emphasizing the distribution of Hadean zircons. Note that the number of each star represents the order number in Table 1 (see Table 1 for details). Stars 2, 6, 7, and 8 are the Hadean zircons located within the NCC. (b) Subdivision of the NCC and the geological map of the Liaodong Peninsula (modified after Zhao et al., 2005). GEOLOGICAL SETTING canic successions are called the Macheonayeong Group in North Korea (Zhao et al., 2005), the Liaohe Group in the The NCC is one of the oldest continental nuclei on Earth, Liaodong Peninsula (Li et al., 2011), the Laoling and Ji’an being bounded to the north by the Paleozoic Central Groups in southern Jilin (Lu et al., 2006), and the Fen- Asian Orogenic Belt and to the south by the Qinling–Da- zishan and Jingshan Groups in the Shandong Peninsula bie–Su–Lu Orogenic Belt. It formed by assembly of the (Tam et al., 2011). The Liaohe Group consists of three Eastern and Western blocks along the Trans–North China rock units: (1) an arkose– and volcanic–rich sequence in Orogen as shown in Figure 1b (Zhao et al., 2005). The the lower part (the Langzishan, Lieryu and Gaojiayu For- Eastern Block consists of the Longgang Block and the mations), (2) a carbonate–rich sequence in the middle (the Nangrim Block, with the Paleoproterozoic JLJB in be- Dashiqiao Formation), and (3) a pelitic sequence in the tween. The two blocks are underlain by the Archean base- upper part (the Gaixian Formation), experiencing amphib- ment (Liu et al., 1992; Song et al., 1996; Wu et al., 1997, olite facies metamorphism (Li et al., 2014a, 2014b; Li et 2005). The NE–trending Paleoproterozoic JLJB is com- al., 2015a, 2015b). The Dashiqiao Formation is composed posed of deformed sedimentary and volcanic successions dominantly of dolomitic marbles intercalated with minor and felsic–mafic intrusions that were metamorphosed carbonaceous slates and mica schists, hosting the largest to greenschist–amphibolite facies at ~ 1.9 Ga as shown magnesite deposit in the world and notable for its thick in Figure 1 (Luo et al., 2004; Li et al., 2005; Lu et al., and pure orebody (Tang et al., 2009, 2013). Our sample 2006; Li and Zhao, 2007; Luo et al., 2008; Meng et al., (LHZ1) belongs to the Dashiqiao Formation as described 2014; Li et al., 2015a, 2015b). The sedimentary and vol- below. Hadean detrital zircon 285 Table 1. Distribution of the Hadean zircons on Earth * SHRIMP, sensitive high resolution ion microprobe; CAMECA, Cameca Ion Microprobe; LA–ICP–MS, laser ablation–inductively coupled plasma–mass spectrometry. SAMPLE DESCRIPTION AND further purified by hand–picking under a binocular mi- ANALYTICAL METHOD croscope. The zircons were set in an epoxy mount that was polished and then vacuum–coated with a layer of 50 Sample LHZ1 (GPS location: 42°33′12′′N, 129°40′37′′E) nm high–purity gold. Cathodoluminescence (CL) images is a staurolite–garnet–mica schist collected from the Da- were taken to examine the internal structure of the indi- shiqiao Formation in the Dashiqiao magnesite deposit vidual grains. The zircon U–Pb analysis was performed of Dashiqiao City, Liaoning Province. It is dark gray in using the LA–ICP–MS housed at Tianjin Institute of color, with a lepido–granoblastic texture and schistosity. Geology and Mineral Resources, China. This unit is a It contains staurolite (10%) + garnet (15%) + biotite Neptune ICP–MS equipped with a 193 nm Geolas Q Plus (30%) + muscovite (15%) + plagioclase (20%) + quartz ArF exciplex laser ablation. The laser spot diameter and (10%) and accessory epidote, magnetite, apatite, and zir- frequency were 32 µm and 10 Hz, respectively. A zircon con. The schist is intercalated with dolomitic marbles. GJ–1 was employed as an external standard for age cal- The field relations are shown in Figure 2. Geochemically, ibration, the standard glass NIST 610 was used to opti- the staurolite–garnet–mica schist consists of SiO2 = 55.77 mize the machine, and a zircon TEMORA was used as 207 206 206 238 wt%, Al2O3 = 15.30 wt%, Fe2O3 = 3.19 wt%, FeO = 7.20 a monitoring standard. The Pb/ Pb, Pb/ U, and 207 235 wt%, and K2O = 2.95 wt%. Using a petrological and geo- Pb/ U ratios and apparent ages were calculated using chemical classification, its protolith is classified as shale the GLITTER 4.0 program (Jackson et al., 2004). The (see Li et al. 2015b). measured compositions were corrected for common Pb The zircon grains from Sample LHZ1 were extract- using the measured non–radiogenic 204Pb (Andersen, ed using heavy liquid and magnetic methods and were 2002). The age calculations and the plotting of the con- 286 Z. Li, B. Chen and C. Wei Figure 2. Photos of the sample local- ity. (a) A field photo showing that the schist (d) is intercalated with dolomitic marbles (b) and (c). (e) Microphotograph of the stauro- lite–garnet–mica schist (LHZ1). cordia diagram were done using ISOPLOT 3.0 (Ludwig, bright and has irregular shapes, which could be attributed 2003). The uncertainties for individual LA–ICP–MS anal- to later overgrowth of the crystal, similar to the one with yses are quoted at the 1σ level, with errors on pooled ages Archean age (see #21 in Fig. 3a). Unfortunately, the rim is quoted at the 95% (1σ) confidence level. Details of the too narrow to measure the U–Pb age data; therefore, we technique are described by Yuan et al. (2004). are not able to unequivocally distinguish whether the rim is an igneous or a metamorphic overgrowth.
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