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    SHRIMP U-Pb zircon geochronology of the Fuping Complex implications for formation and assembly of the North China Craton [查看] HongGuan、MinSun、SimonA.Wilde、XinhuaZhou、MingguoZhai
    The Fuping Complex, located within the central zone of the North China Craton, is composed of amphibolite to granulite facies orthogneisses, interleaved with minor supracrustal rocks at similar metamorphic grade. The oldest components recognised are hornblende gneiss enclaves within the predominant biotite orthogneiss which have a SHRIMP U–Pb zircon age of 27088 Ma. We consider these enclaves to represent fragments of ~2.7 Ga continental materials incorporated in the biotite gneiss. The biotite gneiss has a SHRIMP U-Pb zircon age of 2513±12 Ma, interpreted to be time of magmatic crystallisation of the igneous precursor, based on the igneous characteristics of the zircons. This indicates a major magmatic episode at 2.52 Ga in the Fuping Complex, identical to the age of felsic volcanism within the low-grade Wutai Complex which crops out immediately to the west. A gneissic granite that intrudes the biotite gneisses has a poorly-defined 207Pb/206Pb age of 2045±64 Ma. This is within error of the age of 2097±46 Ma obtained from a fine-grained gneiss interlayered with amphibolite of the Wanzi Supracrustal Suite (WSS), interpreted to be volcanic in origin. Zircons from both these samples have strong oscillatory zoning and provide the first indication of a Palaeoproterozoic magmatic event in the area, again similar in age to magmatic events recently recognised in the adjacent Wutai Complex. These data indicate a comparable history for the Fuping and Wutai Complexes and support geochemical evidence that they had a common origin and formed part of a Late Archaean arc, affected by later Palaeoproterozoic re-activation. Low-uranium zircons without oscillatory zoning, separated from a sample of biotite gneiss, yield data clustered at 181726 Ma, which is interpreted to reflect a period of new zircon growth during a major metamorphic event. These data support the recently-proposed tectonic model that amalgamation of the North China Craton occurred due to collision of the Eastern and Western Blocks along the central zone at 1.8 Ga ago.
    Tectonic setting and significance of 2.3-2.1 Ga magmatic events in the Trans-North China Orogen New constraints from the Yanmenguan mafic-ultramafic intrusion in the Hengshan-Wutai-Fuping area [查看] ZhihongWang、SimonA.Wilde、JialiangWan
    Adetailed study of the∼2.2 GaYanmenguan mafic–ultramafic intrusion in the Hengshan area is presented with the aim of clarifying the tectonic history of the Trans-North China Orogen in the North China Craton during the period 2.3–2.1 Ga. SHRIMP U–Pb dating of magmatic zircons from a gabbro indicates emplacement at ∼2193 Ma. The whole rock and mineral geochemistry of this intrusion are akin to Alaskan-type complexes, and are typical of subduction-related magmas. The parental magma likely originated from the depleted mantle wedge above a subduction zone, and experienced fractional crystallization of olivine and clinopyroxene. The continental arc, represented by the mafic–ultramafic intrusions and contemporary granitic and volcanic rocks, together with the Lüliang back-arc basin constitute a marginal arc–back-arc basin system that evolved between 2.3 and 2.1 Ga. Based on geochronological datasets and available data on magmatism, metamorphism and structural deformation, a comprehensive new tectonic model for the evolution of the TNCO during the Neoarchean to Paleoproterozoic is constructed: (1) ∼2.5 Ga intra-oceanic arc–back-arc basin system and its accretion at the end of the Neoarchean; (2) a long hiatus in magmatism and tectonism between ∼2.5 and 2.3 Ga; (3) ∼2.3–2.1 Ga marginal arc–back-arc basin magmatism developed in the accreted Hengshan–Wutai–Fuping arc terranes and the Lüliang terrane;(4) ∼2.1 Ga collision, resulting in closure of the ∼2.3–2.1 Ga Lüliang back-arc basin, accretion of the Lüliang–Hengshan–Wutai–Fuping arc terranes, and their attachment to the Western Block of the North China Craton; (5) the intrusion of ∼1970–1910Ma post-collisional mafic dykes in an extensional event;(6) final collision between the Western and Eastern Blocks between∼1.9 and 1.8 Ga, resulting in extensive magmatism, tectonism and metamorphism; and lastly (7) post-1.8 Ga crustal extension.
    Combined U-Pb, hafnium and oxygen isotope analysis of zircons from meta-igneous rocks in the southern North China Craton reveal multiple events in the Late Mesoarchean-Early Neoarchean [查看] DunyiLiu、SimonA.Wilde、YushengWan、ShiyanWang、JohnW.Valley、NorikoKita、ChunyanDong、HangqiangXie、ChangxiuYang、YixinZhang、LinzhiGao
    We report the results of a comprehensive isotopic investigation of zircons from metamorphosed tonalites and amphibolites from Lushan in the far south of the Trans-North China Orogen of the North China Craton that reveal the oldest rocks yet dated from the orogen. A detailed investigation of the internal structures of zircons, combined with targeted SIMS U–Pb and oxygen isotope analyses and ICP-MS Hf zircon analyses, has resulted in the discovery of previously unknown geological events in the North China Craton. Magmatic zircon from the tonalite and amphibolite was found to be essentially coeval with a small spread of ages from 2829±18Ma to 2832±11 Ma in the tonalites and from2838±35 Ma to 2845±23Ma in amphibolite. Hafnium isotope data suggest derivation of both tonalite and amphibolite from a depleted mantle source with minor crustal contamination. Oxygen isotope ratios in zircons range from 5.1 to 7.3‰ VSMOW, with high δ18O results recorded only from metamorphic domains. The earliest stage of metamorphic zircon growth, present in all four samples analyzed in this study, occurred between 2772±17/22 in the tonalites and 2776±20 and 2792±12 Ma in the amphibolites. A younger metamorphic event at 2638±61 in the tonalite and between 2671±13 and 2651±13 Ma in the amphibolites is recognized in zircons from three of the four samples investigated. This is the first time that metamorphic events at either of these times have been recorded in the North China Craton. Importantly, there is no evidence for the 1.8 Ga high-grade metamorphic event that is manifest in the northern and central parts of the Trans-North China Orogen.
    SHRIMP U-Pb zircon dating of the Wulian complex Defining the boundary between the North and South China Cratons in the Sulu Orogenic Belt,China [查看] Jian-BoZhou、SimonA.Wilde、Guo-ChunZhao、Xing-ZhouZhang、Chang-QingZheng、WeiJin、HongCheng
    Neoproterozoic metasedimentary and metavolcanic rocks of the Wulian Group are associated with gneissic granitoids at the northern margin of the Sulu UHP Belt,adjacent to the Wulian-Yantai Fault,and are collectively referred to as the Wulian complex,SHRIMP U-Pb dating of detrital zircon from the metasedimentary rocks of the Wulian Group indicates a range in age from 3478 to 625Ma.Based on zircons＜10% discordant,they can be broadly divided into four populations:＞3000Ma，with the oldest age being 3339Ma;2700~2400Ma,with a peak at 2436Ma;2200-1800Ma,with a peak at ~2156Ma;and at ~770Ma.These results indicate that deposition of the Wulian Group was after ~770Ma and that some detrital material most likely came from Neoproterozoic sources in the South China Craton(SCC).SHRIMP U-Pb zircon dating of a metavolcanic rock defines a weighted mean 206Pb/238U age of 761±8Ma，which is consistent with other rocks of South China affinity and can be correlated with syn-rift magmatism during the breakup of the supercontinent Rodinia.The Wulian Group,together with Neoproterozoic granites of the Wulian complex,constrains the location of the Triassic suture zone betwwen the North China and South China Cratons,Based on our new data,the suturemust lie north of the Wulian complex and is marked by the Baichihe-Yantai Fault.
    SHRIMP U–Pb zircon dating of the Neoproterozoic Penglai Group and Archean gneisses from the Jiaobei Terrane,North China, and their tectonic implications [查看] Jian-BoZhou、SimonA.Wilde、Guo-ChunZhao、Chang-QingZheng、WeiJin、Xing-ZhouZhang、HongCheng
    Archean basement gneisses and supracrustal rocks, together with Neoproterozoic (Sinian) metasedimentary rocks (the Penglai Group) occur in the Jiaobei Terrane at the southeastern margin of the North China Craton. SHRIMP U–Pb zircon dating of an Archean TTG gneiss gave an age of 2541±5 Ma, whereas metasedimentary rocks from the Neoproterozoic Penglai Group yielded a range in zircon ages from 2.9 to 1.8 Ga.The zircons can be broadly divided into three age populations, at: 2.0–1.8 Ga, 2.45–2.1 Ga and >2.5 Ga. Detrital zircon grains with ages >2.6 Ga are few in number and there are none with ages <1.8 Ga. These results indicate that most of the detrital material comes from a Paleoproterozoic source, most likely from the Jianshan and Fenzishan groups, with some material coming from Archean gneisses in the Jiaobei Terrane. An age of 1866±4Ma for amphibolite-facies hornblende–plagioclase gneiss, forming part of a supracrustal sequence within the Archean TTG gneiss, indicates Late Paleoproterozoic metamorphism. Both the Archean gneiss complex and Penglai metasedimentary rocks resemble previously described components of the Jiao-Liao-Ji orogenic belt and suggest that the Jiaobei Terrane has a North China Craton affinity; they also suggest that the time of collision along the Jiao-Liao-Ji Belt was at ∼1865 Ma.
    SHRIMP U–Pb zircon ages of granitoid rocks in the Luliang Complex Implications for the accretion and evolution of the Trans-North China Orogen [查看] GuochunZhaoa、SimonA.Wilde、MinSun、SanzhongLi、XupingLi、JianZhang
    The lvliang Complex is situated in the central segment of the Trans-North China Orogen (TNCO), a continent-continent collisional belt along which the discrete Eastern and Western Blocks amalgamated to form the basement of the North China Craton. The complex consists of supracrustal and granitoid rocks, of which the latter can be subdivided into pre-tectonic TTG gneisses, including the Yunzhongshan, Guojiazhuang and Chijianling–Guandishan gneisses; syn-tectonic gneissic granites represented by the Huijiazhuang gneissic granite; and post-tectonic granites,including the Luyashan charnockite, Luchaogou porphyritic granite and Tangershang/Guandishan massive granite. The pre-tectonic TTG gneisses are mostly calc-alkaline and considered to have formed in a magmatic arc environment. SHRIMP U–Pb analyses reveal that the Yunzhongshan gneisses were emplaced at ∼2499±9 Ma, representing the earliest arc-related magmatic event in the Luliang Complex. This was followed by the intrusion of the Guojiazhuang gneisses at 2375±10 Ma. The most widespread arc-related magmatic event in the region was the emplacement of the Chijianling–Guandishan granitoid gneisses, of which the tonalitic, granodioritic and monzogranitic gneisses were emplaced at 2199±11 Ma,2180±7Ma and 2173±7 Ma, respectively. Metamorphic zircon overgrowth rims from a tonalitic gneiss yielded a weighted mean 207Pb/206Pb age of 1872±7 Ma, consistent with the metamorphic age range of 1880–1820 Ma defined by metamorphic zircons from various high-grade rocks in the TNCO. Thus, the evolution of the lvliang Complex involved emplacement of the Yunzhongshan granitoids at ∼2499 Ma, the Guajiazhuang granitoids at ∼2375 Ma and the Chijianling–Guandishan granitoids at 2199–2173 Ma, with the final collision between the Eastern and Western Blocks in this area occurring at 1872±7 Ma, the whole series of magmatic events lasting nearly 650 Ma. This suggests that the Trans-North China Orogen represents a long-lived magmatic arc. The new SHRIMP zircon data, combined with structural and petrological studies, also reveal the existence of both syn- and post-collisional granites in the Luliang Complex. The former is represented by the Huijiazhuang gneissic granite that was emplaced at 1832±11 Ma, whereas the latter include the 1815±5Ma Luyashan charnockite, 1807±10 Ma Luchaogou porphyritic granite,1798±11 Ma Guandishan massive granite and 1790±14 Ma Tangershan massive granite.
    SHRIMP U-Pb and CAMECA 1280 oxygen isotope results from ancient detrital zircons in the Caozhuang quartzite, Eastern Hebei, North China Craton Evidence for crustal reworking 3.8 Ga ago [查看] SIMONA.WILDE、JOHNW.VALLEY、NORIKOT.KITA、AARONJ.CAVOSIE、DUNYILIU
    ABSTRACT. The Caozhuang quartzite, located in Eastern Hebei Province in the eastern part of the North China Craton, has long been known to contain the oldest detrital zircon population in China. A suite of 30 zircons with preliminary ages >3.7 Ga were selected for detailed SHRIMP U-Pb and CAMECA 1280 oxygen isotope analyses.SHRIMP U-Pb dating reveals that ages range from 3860 to 3135 Ma, the former being the oldest 207Pb/206Pb zircon age so far obtained from the North China Craton. Values of 18O range from 5.4 to 7.5 permil, similar to Archean igneous zircons worldwide, but the average value for the 30 zircons is 6.6 permil, which is 0.3 permil higher than suite averages for detrital zircons from the Jack Hills and Beartooth Mountains and nearly 1 permil higher than magmatic zircons from igneous rocks of the Superior Province and Barberton. These elevated values of 18O suggest reworking of a significant amount of juvenile crust, older than 3.8 Ga, that underwent a low temperature supracrustal history and was distributed throughout the source region in northeast China.
    NEW U-Pb AND Hf ISOTOPIC DATA CONFIRM ANSHAN AS THE OLDEST PRESERVED SEGMENT OF THE NORTH CHINA CRATON [查看] DUNYILIU、SIMONA.WILDE、YUSHENGWAN、JIASHANWU、HONGYINZHOU、CHUNYANDONG、XIAOYANYIN
    ABSTRACT. The Anshan area in the northeastern part of the North China Craton contains the oldest known rocks in China. Rocks with ages of 3.8 Ga are present in three trondhjemite-dominated gneiss complexes, referred to as the Baijiafen, Dongs-han and Shengoushi complexes. The oldest material identified in these complexes has weighted mean 207Pb/206Pb ages of 3800 5 Ma, 3794 4 Ma and 3777 13 Ma,respectively. In addition, younger geological events at 3680 19 Ma, 3620 23 Ma, and 3573 21 Ma have been identified, recording the emplacement of several generations of trondhjemite. A biotite schist of possible supracrustal origin contains a zircon population with a weighted mean 207Pb/206Pb age of 3723 17 Ma and is cut by a 3620 Ma trondhjemite, implying formation prior to3.62 Ga. TDM(Hf) model ages for the zircons range from 3256 to 4264 Ma, but are mostly 3.9 Ga, indicating that significantly older crust was not present in the source region of the trondhjemitic magmas.
    Metamorphism in the Central Zone of the North China Craton SHRIMP U-Pb dating of zircon from metamorphic rocks in the Lushan area, Henan Province [查看] YushengWan、SimonA.Wilde、DunyiLiu、ChangxiuYang、BiaoSong、XiaoyanYin
    This paper reports SHRIMP zircon U–Pb dating of Precambrian supracrustal and granitic rocks from the Lushan area, Henan Province, in the southern portion of the Central Zone (also referred to as the Trans-North China Orogen) of the North China Craton. A graphite–garnet–sillimanite gneiss (Sample TW0006/1) of the Shangtaihua F Group gives a range of inherited zircon ages from 2.73 to 2.26 Ga and a metamorphic zircon age of 1.84±0.07 Ga. A garnet-bearing gneissic granitoid (Sample TWJ358/1), which is considered to intrude the Shangtaihua F Group, gives a magmatic zircon age of 2.14±0.02 Ga and a metamorphic zircon age of ¨1.87 Ga. The metamorphic zircon ages of 1.87–1.84 Ga obtained in this study indicate that an important tectonothermal event occurred at the end of the Paleoproterozoic in the Lushan area. This supports the southern continuation of a Central Zone in the North China Craton that workers have recently considered to result from continent–continent collision. It is also evident that the Shangtaihua FGroup_ was formed during the Paleoproterozoic (between 2.26 and 2.14 Ga), and not during the Archean, as previously considered.
    Implications based on the first SHRIMP U-Pb zircon dating on Precambrian granitoid rocks in North Korea [查看] GuochunZhao、LinCao、SimonA.Wilde、MinSun、WonJongChoe、SanzhongLi
    Precambrian basement rocks in North Korea consist of supracrustals and granitoid rocks, of which the former comprise the late Archean Nangrim Group and the Paleoproterozoic Jungsan andMachollyong Groups, whereas the latter include four major types: grey TTG gneisses, garnet/sillimanite-bearing (S-type) granites,massive porphyritic granites, and hornblende-bearing granites. SHRIMP U–Pb zircon geochronology, combined with cathodoluminescence (CL) imaging has enabled for resolution of magmatic and metamorphic events that can be directed towards understanding the Precambrian history of North Korea and its relations toNorth China. SHRIMP U–Pb zircon analyses on two grey gneiss samples (PO501 and K14) reveal that they were emplaced at 2538±14 Ma and 2636±49 Ma,respectively, and metamorphosed at 2462–2433 Ma. These data, for the first time, confirm the existence of late Archean rocks in the Korean Peninsula.Moreover, one grey gneiss sample (K14) contains several zircons with ages of 3.1–3.4Ga, suggesting possiblemiddle Archean crust in North Korea. Rocks with such ages are widely distributed in North China, implying that North China and North Korea have similarArchean basement.One grey gneiss sample (R53) yielded a SHRIMP zircon age of 1933±12Ma, indicating that some grey gneisses in North Korea formed during the Paleoproterozoic. Two garnet- and/or sillimanite-bearing S-type granite samples gave 207Pb/206Pb ages of 1908±31Ma and 1903±49Ma, interpreted to reflect the time ofmetamorphismof the Paleoproterozoic Jungsan and Machollyong Groups since these S-type granites are considered to be derived fromthe partialmelting of pelitic rocks fromthese groups. The∼1.9Gametamorphic event has also been revealed in Paleoproterozoic rocks in South Korea and NorthChina. SHRIMP zircon data also show that massive porphyritic monzogranites inNorth Korea evolved over a protracted interval from1865Ma to 1843Ma. Similaraged porphyritic monzogranites are also found in North China and South Korea, and their origin is considered to be related to a posttectonic extensional event of regional extent. The last phase of Precambrian magmatism recognized in North Korea is Grenvillian-aged,represented by the hornblende-bearing granite that yields a SHRIMP zircon age of 1195±4Ma, and is considered to be the source rock of the adjacent Yushulazi Group (North China) that contains numerous 1.1–1.2 Ga old detrital zircons.
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