15 July 2022, Volume 45 Issue 2

    

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The 60th Anniversary Special Issue(The Study of Precambrian Geology)
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  Four stages A-type granitoids in Shandong Province and their implications for tectonic evolution

  WANG Bin, SONG Ming-chun, ZHOU Jian-bo, DING Zheng-jiang, BAO Zhong-yi, LV Jun-yang, WANG Shan-shan

  North China Geology. 2022, 45(2): 1-17. https://doi.org/10.19948/j.12-1471/P.2022.02.01

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  Multi-stage geological tectonic process and multi-geodynamic background lead to the complex tectonic evolution in Shandong Province. Since the Middle Archean, the Shandong area has been characterized by strong magmatic activity, wide distribution of granites, clear evolutionary sequence and diverse formation ages, and is an important geological basis for studying the crustal evolution of the Shandong area. This paper studies the rock assemblage, geological characteristics, geochemical characteristics, genesis, material sources and tectonic setting of the Neoarchean, Neoproterozoic, Triassic and Cretaceous potassic granites in Shandong area. These granites are all A- type granites, which occurred at the end of each crustal movement stage, and are the key markers of crustal evolution and tectonic transition in Shandong area and North China Craton. Among them, the Neoarchean Sihaishan granitoid in Linyi is A2- type granite, which belong to the post- orogenic extensional environment granitoids of Archean microcontinent continental or arc-continent collision. Lanshantou granitic gneiss is A2-type granites in early stage and A1- type granites in late stage, which is a Neoproterozoic non- orogenic extensional granitic gneiss associated with the breakup of the Rodinia supercontinent. The Shidao granitoid in Weihai is A2-type granitoid in the post-orogenic extensional environment of the continental collision between the Yangtze plate and the North China Plate in the Triassic. The Cretaceous Laoshan granitoid in Qingdao and Dadian quartz syenite in Rizhao are composed of early A2- type and late A1- type granites, which are granites in non- orogenic extensional environment and are important markers after the peak stage of craton destruction.
  
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  Precambrian geology and geoparks in Shandong province, China

  WANG Shi-jin, WAN Yu-sheng

  North China Geology. 2022, 45(2): 18-36. https://doi.org/10.19948/j.12-1471/P.2022.02.02

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  Precambrian strata in the Shandong Province include the Neoarchaean Taishan Group Complex and Yishui Group Complex, the Neoproterozoic Tumen Group distributing in the Western Shandong Province, the Neoarchaean Jiaodong Group Complex, the Paleoproterozoic Jingshan Group and Fenzishan Group, the Mesoproterozoic Zhifu Group, the Neoproterozoic Penglai Group in the Eastern Shandong Province, and the Paleoproterozoic metamorphic supracrustal rock assemblage and the Mesoproterozoic Wulian Group in the Jiaonan- Weihai Orogen. The Precambrian intrusive rocks in the Shandong Province are mainly the three phase Neoarchaean intrusive rocks outcropped in the western Shandong Province, starting from mantle-source magma for each phase. The early phase tectono- magmatism resulted in the intrusion of protoliths of the～2 700 Ma tonalitic gneiss, banded tonalitic gneiss. The middle phase tectono-magmatism is dominated by the 2 630～2 600 Ma trondhjemite- tonalite- granodiorite suite. The late phase mantle- sourced magmatism produced the Yishan Series trondhjemite- tonalite- granodiorite suite; the crustal anatexis produced the Aolaishan Series monzonitic granite, leading the formation of a large scale continental crust. There occurred 2 900 Ma (Mesoarchaean) tonalitic gneiss and trondhjemitic gneiss in the eastern Shandong Province, relatively a large scale 2 700 Ma (early Neoarchaean) tonalitic gneiss, banded tonalitic gneiss, 2 500 Ma (late Neoarchaean) trondhjemite-tonalite-granodiorite suite and monzonitic granite, the late Paleoproterozoic monzonitic granite and ultramafic- mafic rocks. In the Su- Lu Orogen of the eastern Shandong Province, there occurred the Neoproterozoic ultramafic-mafic rocks and the tonalitic- granodioritic- monzonite- granitic gneiss. The geoparks characterized by the Archaean geology are mainly distributed in the western Shandong Province, including the geoparks of Mount Tai, Mount Meng, Mount Yi, Mount Lu and the Shuilianxia Canyon in Jinan, Changchengling Range and Longwan Bay in Taian, Mount Niu in Feicheng, Mount Yi in Linqu, Fangganjiulong Canyon in Laiwu, Mount Qingyun in
  Xintai, Mount Longmen in Sishui, Mount Lianqing in Qingzhou, Dianzi in Shanting District of Zaozhuang, Mount Shimen in Wufu, etc. The geoparks marked by the Proterozoic geology in the Shandong Province include the national geoparks of the Changdao island and the Mounts Wulian- Jiuxian, the provincial geoparks of the Mount Jiazi of Lingang in Linyi, Liugong Island in Weihai and Mount Kunyu in Yantai, and the Mount Fulai Geoheritage Protection Area in Ju county.
  
  
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  Redefinition of jiehekou group in Yunzhongshan area, Shanxi province

  KANG Jian-li, WANG Hui-chu, CHEN Feng, ZENG Le, SUN Yi-wei, XIAO Zhi-bin, TIAN Hui

  North China Geology. 2022, 45(2): 37-50. https://doi.org/10.19948/j.12-1471/P.2022.02.03

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  Yunzhongshan lies between Wutai area andLvliang area, which plays an important role in studying tectonic relationshipbetween Wutai complex and Lvliang complex. The metamorphic basement inYunzhongshan is mainly composed of Neoarchaean granitic gneisses and a suit ofmetamorphosed supracrustal rocks which was called“Jiehekou Group”consisting ofquartzite, Bi- leptynite, marble and amphibolite. However, according to fieldinvestigation, there are many differences between these metamorphosedsupracrustal rocks and the typical Jiehekou Group in Lvliang area. Based on therock association in this field investigation, these metamorphosed supracrustalrocks are divided into two parts. Ar3Y (Y represents Yunzhongshan metamorphosedsupracrustal rocks) resided in the Neoarchaean granitic gneisses containsBi-leptynite, quartzite, Hb-leptynite, amphibolite and so on. Chronologicalstudy of the granitic gneisses shows that the forming age of Ar3Y is older than~2.5 Ga; Pt1qz (qz represents quartzite) has a ductile shearing contact withthe Neoarchaean granitic gneisses, part of which is intruded by latePaleoproterozoic intrusions aging of ~1.94 Ga. Pt1qz consists largely ofquartzite, magnetite leptynite, marble and amphibolite. The research ofgeochronology implies the formation age of Pt1qz is 1.94~2.14Ga. Thegeochemistry of the metavolcanics rocks in two suits of metamorphosedsupracrustal rocks respectively suggest that Pt1qz was formed in the backgroundof spreading tectonics with the products of passive continental margin and Ar3Ywas developed in an island arc environment of subduction zone.

  
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  SHRIMP Zircon U-Pb Geochronology of the Tuffite Layer in the Shi’nagan Group, Inner Mongolia, North China Craton

  SU Wen-bo, LI Wen-guo, LI Hui-min, SONG Biao, DI Yong-jun, ZHOU Hong-ying, WANG Hui, WANG Jian, Frank R Ettensohn, Warren D Huff

  North China Geology. 2022, 45(2): 51-67. https://doi.org/10.19948/j.12-1471/P.2022.02.04

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  For the first time, the age of aninterbedded tuffite layer and related volcanogenic deposits have been determinedfrom the middle of the Lower Formation of the Shi’nagan Group, near DashetaiTown, Urad Front Banner, Inner Mongolia. Using SHRIMP zircon U-Pb ages for thetuffite layer, Sample NM-1191, the weighted mean 207Pb/206Pb age of 1 614±8 Ma(n=21, 95% conf., MSWD = 0.17) was obtained, which precisely calibrates the timeof the corresponding volcanic eruption event. Hence, on the whole, theShi’nagan Group was probably deposited during the transitional time interval atthe end of the Paleoproterozoic Statherian Period (i.e., the ChangchengianPeriod of China, 1 800~1 600 Ma) to the beginning of the MesoproterozoicCalymmian Period (i.e., the Jixianian Period of China, 1 600~1 400 Ma). Thisnew revision of the chronostratigraphy indicates that,during the Paleo-Mesoproterozoic transition interval, all the three groups (i.e., the Shi’naganGroup, the Zha’ertai Group, as well as the Bayan-Obo Group) in Inner Mongoliawere very likely contemporaneous, heterotopic facies that existed side-by-side.In addition, our dating shows that the Shi’nagan Group can be correlated fairlywell with the Dahongyu and the Gaoyuzhuang formations in the Yanshan (Yanliao)and the Taihang mountains from the northern to the middle parts of the NorthChina Craton (NCC), respectively. Furthermore, this agemeans that the Shi’naganGroup may also be equivalent to the Luoyukou and the Longjiayuan formations onthe south margin of the NCC. Moreover, in combination with regional geologicalinformation, it may be inferred that both the Huangqikou and the Wangquankouformations at the western margin of Ordos Block and the First and Secondformations of the Dunzigou Group in the Longshoushan Mountains at the southmargin of the Alxa (Yinshan) Block, might be coeval with the Shi’nagan Group.Consequently, this kind of widespread correlation may imply that, at leastuntil to the beginning of the Calymmian Period, the Alxa Block was probablyaffiliated with the NCC, which was covered by the vast“Pan-NCC”epicontinentalsea, including the south margin of Alxa Block, the west margin of Ordos Block,the Yanshan (Yanliao)- Taihang basins, as well as the Xiong’er Basin.The agecalibration of the Shi’nagan Group and the related revised stratigraphicframework will provide critical chronological constraints for some majorissues, including the reinterpretation of the depositional and tectono-paleogeographyof the north margin of NCC, the relationship of the NCC to the ColumbiaSupercontinent, and other related issues during the Paleo-Mesoproterozoictransitional interval.

  
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  Geological significance of two-phase isotopic ages of Paleoproterozoic mafic granulites in Jining area

  CHANG Qing-song, SHI Jian-rong, ZHANG Jia-hui, WANG Hui-chu, REN Yun-wei

  North China Geology. 2022, 45(2): 68-75. https://doi.org/10.19948/j.12-1471/P.2022.02.05

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  Paleoproterozoic mafic granulites have been one of the research hotspots in tectonic revolution of North China Craton. Recent 1/50000 regional geological survey in which the author has participated has shown that there are two phases of age information for the Paleoproterozoic mafic granulites in Jining area. The early phase is 1.96 Ga~1.91 Ga, which records the evolution of emplacement of the protoliths of the mafic granulites, the ultra- high temperature metamorphic of the khondalites and origin of the remelted granites and the simultaneously granulite-high amphibolite facies metamorphism. This phase of magmatic event, together with the regional ~1.95 Ga high-pressure granulite metamorphic ages, records the evolution of the orogenic collision-post-collisional extension. The later phase is the 1.85 Ga~1.80 Ga metamorphic age, possibly indicating the widespread influence of the ~1.85 Ga extrusive orogenic event.
  
  
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  Petrogenesis and geodynamic settings of monzonitic granite at the end of the Neoarchean in Tianzhen-Huai'an area

  REN Yun-wei, ZHANG Jia-hui, TIAN Hui, WANG Hui-chu, SHI Jian-rong, CHANG Qing-song, ZHANG Kuo

  North China Geology. 2022, 45(2): 76-86. https://doi.org/10.19948/j.12-1471/P.2022.02.06

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  Through detailed field geological work around Huaian- Tianzhen area, a suite of monzogranites has been distinguished from the TTG gneiss in the Huai’an complex. The zircon U-Pb ages of one monzogranite sample are 2 472±10 Ma and 2 448±9 Ma respectively obtained through LA-ICP-MS and SHRIMP methods. The contents of SiO2, Al2O3, K2O, Na2O and K2O are 70.55%～74.29%, 13.78%～15.35%, 4.26%～5.74% and 3.04%～4.58% respectively. The samples are attributed to potash granite with K2O / Na2O=1.29～1.89, except for only one with K2O / Na2O=0.93. The contents of Cao, MgO, TFeO and TiO2 of the monzogranite are 1.02%～1.37%, 0.15%～0.47%, 0.76%～1.9% and 0.16%～0.32% respectively, indicating enrichment in elements of Si, Na, K, Al, and depletion in elements of Ca, Fe, Mg, Ti. In addition, the monzogranite show relative enrichment in LREE (Rb, Ba, K and Sr) and depletion in HREE (U, Nb, Ta, P and Ti), with higher content of Th and lower content of Cr and Ni, indicating similar REE and trace elements characteristics with the middle- upper crust. The samples with higher content of Sr and lower content of Y and Yb are supposed to be formed in condition with middle to high pressure. Based on the above, the monzogranite in Huai'an complex should be product of partial melting of thickened lower crust, indicating the continental crust of the northern margin of North China Craton was mature and had already accomplished its cratonization in late Neoarchean.