31 March 2023, Volume 46 Issue 1

    

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  The temporal and spatial distribution characteristics of intrusive rocks in the border area between China and Mongolia and its implications for tectonic evolution

  FU Chao, LI Jun-jian, ZHANG Shuai, DANG Zhi-cai, TANG Wen-long, Orolmaa Demberel

  North China Geology. 2023, 46(1): 1-19. https://doi.org/10.19948/j.12-1471/P.2023.01.01

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  The border area between China and Mongolia developing various types of intrusive rock is an important part of the complex tectonic environment in the Central Asian orogenic belt. In the area, rock type and rock combination rich variety with a large age span. Discussing the temporal and spatial distribution characteristics and establishing intrusive rock framework has important significance in understanding the regional tectonic evolution and crust mantle activity. Taking the magmatic cycle as the main line, the paper compared the spatial and temporal characteristics of intrusive rock between the Lvliangian to the Yanshanian, that clearly reflects the "active" in the crust collision and suturing began in the Caledonian and reached its peak in the Variscan. This indicates that the crust gradually sutures from west to east. The orogenic process differ between western Altay orogenic belt and Eastern Xing'an Mongolian orogenic belt under different tectonic units. In addition, there are large-scale magmatic belts on both sides of the regional fault, and regional faults control the scope and scale of the intrusive rock significantly.
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  Metallogenic regularity and prospecting direction of Tin deposits in North China

  North China Geology. 2023, 46(1): 20-26. https://doi.org/10.19948/j.12-1471/P.2023.01.02

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  Tin resources are abundant in North China, especially in the middle and southern Greater Khingan Range, which is one of the three major tin mining areas in our country and the only formed tin polymetallic ore belt found in the north of China.  The types of tin deposits in North China are mainly divided into three categories: hydrothermal, porphyry and contact account type, most of which are co-occurring and associated deposits, with few independent tin deposits. The mineralization period of tin deposits in the region is mainly concentrated in the Late Jurassic-Early Cretaceous. On this basis, the main ore-controlling factors of tin deposits in North China were analyzed, the metallogenic models of contact metasomatic, porphyry and hydrothermal tin deposits were initially established, and the temporal and spatial distribution of tin deposits were discussed, and Xilinhot- Keshiketeng Banner, Erlian-Dongwu Banner and Shangdu-Taipusi Banner are key areas for searching for tin deposits in North China.
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  The characteristics of chromite deposits and analysis of metallogenic potential in North China

  DANG Zhi-cai, LI Jun-jian, ZHANG Tong, FU Chao, SONG Li-jun, PENG Yi, FANG Tong-ming

  North China Geology. 2023, 46(1): 27-32. https://doi.org/10.19948/j.12-1471/P.2023.01.03

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  In recent years, 49 chromite deposits (ore occurrences) including 1 medium-sized deposit, 11 small-sized deposits and 37 occurrences have been discovered in North China. These chromite deposits (occurrences) are mainly distributed in Inner Mongolia, Hebei, Henan and Beijing provinces，which strictly controlled by Ophiolites and distributed spatially along the ophiolite belts, such as Shangdan, Suolunshan and Hegenshan. They were formed in Archen to Mesozoic, and Neoarchean-Paleoproterozoic and Late Paleozoic were heyday period of chromite mineralization. The ophiolite type is mainly chromite deposit type, followed by magmatic type. The comprehensive analysis shows that several ophiolitic melange belts such as Erlian-Hegenshan, Suolunshan, Kedanshan and Shangdan have good prospecting potential for chromite deposits in Inner Mongolia. Deep exploration and peripheral investigation of known mining areas should be strengthened to achieve a breakthrough in chromite prospecting.
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  Research on tectonic setting of Mesozoic granitoids in the Wuyuan county area, northeastern Jiangxi province

  HU Peng, ZENG Wei, DUAN Ming, WANG Jia-ying

  North China Geology. 2023, 46(1): 33-41. https://doi.org/10.19948/j.12-1471/P.2023.01.04

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  The Bangyankeng, Duanxin and Qingshanling granitic plutons intrude in the eastern part of Jiangnan orogenic belt. The Bangyankeng pluton shows high SiO2 content(65.56%~71.36%), rich in aluminum(Al₂O₃=14.12%~16.58%), and poor in MgO(1.08 to 1.33). It is also rich in potassium(3.42% ~ 4.56%), and weak negative Eu anomaly(δEu=0.65~0.92), (La/Yb)N has a higher value of 13.92~19.09. As the content characteristic element, Y is with a low value of 13.8 ×10^-6 ~17.9×10^-6. Sr is of 335.9×10^-6 ~484×10^-6, with the significant negative anomalies of Nb and Ti. Various characteristics indicate that Bangyankeng granite belongs to C-type adakites with the partial melting of mafic crust formation. The DuanXin and Qingshanling granites are rich in Si, K, poor in Ca, Mg and peraluminous characteristics. The LREE and HREE exhibit moderate right orientation, strong negative anomalies of Eu. It shows classic right-slope"V" shape. The incompatible elements Rb, Th, Ta are high, and Zris slight loss. Ba, Sr, Eu show strong negative anomaly, together with Ga/Al = 3.12~3.44. The geochemistry indicates that DuanXin and Qingshanling rock belong to A2-type granite, as the product of post-orogenic extensional. The crust in northeast of Jiangxi was thickened after the Indosinian orogeny and then suffer the regional tectonic stress shifts during the Late Jurassic to Early Cretaceous.The compression under the tectonic thickening transfers to the post-orogenic extension.
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  Geochemical characteristics, source area properties and tectonic significance of Ore bearing metasedimentary rocks from Tebai gold deposit in Alxa right banner area

  CHENG Xian-yu, TIAN Jian, LI Yi-ke, DONG Man-hua, CAO Kan, ZHANG Tian-fu

  North China Geology. 2023, 46(1): 42-49. https://doi.org/10.19948/j.12-1471/P.2023.01.05

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  In this paper, geochemical analysis of the ore bearing metasedimentary rocks of the Tebai gold deposit in Alxa Right Banner is carried out, The main lithology is mica quartz schist, metamorphic siltstone, metamorphic lithic quartz sandstone, etc; The average content of SiO₂ is 62.39%,the average content of Al₂O₃ is 15.40%, the average content of Fe2O3 is 6.57%, the average content of MgO is 3.84%, the average content of CaO is 2.31%, the average content of K₂O is 2.65%, the average content of Na₂O is 2.09%.The REE patterns of curves are consistent, LREE/HREE=5.75~8.34, the average value is 7.18，（La/Yb）N=5.39~8.38,the average value is 6.83, Eu negative anomaly is obvious, LREE are obviously enriched relative to HREE;  Rb-K2O diagram、Ni-TiO₂ diagram and La/Yb-ΣREE diagram show that the parent rocks may originate from granites; Combined with paleocurrent characteristics and detrital zircon age evidence, it is speculated that the provenance may come from granite in Beidashan area. Combined with the rock assemblage characteristics, tectonic combined characteristics and Geochemical characteristics of Ore bearing metasedimentary rocks in Tebai, it is considered that the source rocks were formed in a tectonic environment of continental island-arc.
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  Review on geological characteristics and mineralization of the Karoo Supergroup, Tanzania

  GONG Peng-hui, LIU Xiao-yang, SUN Kai, WU Xing-yuan, HE Sheng-fei, XU Kang-kang, HE Fu-qing

  North China Geology. 2023, 46(1): 50-60. https://doi.org/10.19948/j.12-1471/P.2023.01.06

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  The Karoo Supergroup in Tanzania represent the earliest Phanerozoic deposition. The stratum is generally continuous, mainly formed in a series of half graben-graben basins that caused by rifting. Based on the comprehensive study of the regional geological distribution, lithologic composition, sedimentary environment analysis and the pollen biological characteristics，the sedimentary sequence, sedimentary facies and the age of sedimentation of each group, section of the Karoo supergroup are systematically studied. The ore-bearing characteristics of this stratum is summarized. According to the study, the lithology of the Karoo Supergroup in Tanzania is generally represented by a suite of sandstone-shale. The deposition time span is from the Late Permian to the Early Cretaceous, and the sedimentary environment from bottom upward is the glacial facies, lake facies and river facies. It is comparable to the typical Karoo Supergroup in South Africa. It also shows good mineralization potential of coal mines and sandstone-type uranium deposits; meanwhile, there are many oil and gas resources, graphite prospecting clues.
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  Review of mantle plume activity and the opening of the East African Rift

  SUN Kai, HE Sheng-fei, LU Yi-guan, ZHANG Hang, XU Kang-kang, GONG Peng-hui

  North China Geology. 2023, 46(1): 61-70. https://doi.org/10.19948/j.12-1471/P.2023.01.07

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  The East African Rift is the most typical continental rift in the world. It is generally believed that the rift consists of two parts: the East Branch and the West Branch. By summing up the previous research results, this paper discusses the relationship between the evolution of the East African Rift and the mantle plume in terms of geophysics, petrology and geochemistry. The models correspond to magmatism with different geochemical properties in northwest Ethiopia and Turkana, respectively. Finally, the possible patterns of the mantle plume under the East African Rift were discussed.
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  Geochemical characteristics and tectonic implications of the Neoproterozoic A-type granites in Red Sea State, Sudan

  North China Geology. 2023, 46(1): 71-79. https://doi.org/10.19948/j.12-1471/P.2023.01.08

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  The Red Sea State of Sudan is located in the Nubian shield. A series of Neoproterozoic granites are identified in the Red Sea State, which consist of medium-coarse- and medium-fine-grained syenogranites and middle-fine-grained alkli feldspar granites. Zircon U-Pb dating implies the granites are intruded in 713 ±4 Ma, which are formed in Pan-African orogenic event. They show high SiO2 contents (70.80%～77.83%). They are metaluminous or weak peraluminous with A/CNK ratios of 0.94～1.08 and A/NK ratios of 1.12～1.44. They show the similar Chondrite-normalized REE and multi-trace elements patterns. The REE patterns are right-inclined with REE medium differentiations of LREE/HREE ratios of 2.46～7.13 and display “V” shaped curve and medium to strong Eu anomaly with δEu values of 0.30～0.57. The granites are characterized by the enrichment of large ion lithophile elements (LILEs) such as Th, U, K and high field-strength elements (HFSEs) such as Zr, Hf and by the depleted Nb, Ta, Sr, P and Ti contents. They show low ISr ratios, depleted εNd(t), εHf(t) values and the similar T_DM1 and T_DM2 values. The granites chemically show A₂-type affinity. We propose that the 713 Ma A-type magmatism might be driven by upwelling of asthenosphere and subsequent partial melts of juvenile crust of Nubian shield on conditions of obvious Heating and decompression in a back-arc extensional setting.
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  Review of research progress on quality assessment methods of 3D geological models

  WANG Yuan-hao, GAO Zhen-ji, SONG Yue

  North China Geology. 2023, 46(1): 80-86. https://doi.org/10.19948/j.12-1471/P.2023.01.09

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  Three-dimensional geological model plays an important role in geological prospecting and resource evaluation, and its quality determines the application potential and effect of the model. This paper reviews the research progress of 3D geological model quality evaluation at home and abroad, and systematically expounds the factors that affect the quality of 3D geological model, including the complexity of modeling geological objects, the accuracy and quality of modeling data sources, the methods of 3D geological modeling, and the expert knowledge of modeling personnel. At the same time, the paper analyzes the principle, advantages and disadvantages of the main methods of quality evaluation of 3D geological models, and holds that the quality evaluation of 3D geological models has gradually entered the era of quantitative evaluation from qualitative evaluation. Finally, this paper summarizes the problems existing in the research of 3D geological model quality assessment methods, and discusses its future development trend.