1. Major crustal movements and tectonic thermal events during the formation of Archean-Proterozoic craton basement.
Archean-Proterozoic is the formation period of the crystalline basement of the Sino-Korean platform, including Yanshan Mountain and its adjacent areas. Many periods of intense regional crustal movements occurred, such as westward movement, Fuping movement, Wutai movement and Lvliang movement. It is accompanied by thermal events such as tectonic deformation in different directions, regional medium-deep metamorphism, volcanic eruption and magmatic intrusion.
1. Move to the west
The crustal movement in Qianxi period was transformed by many crustal movements in the later period, and the late tectonic-thermal events were superimposed. It is difficult to accurately identify the corresponding angular unconformity in the field, but it is still clearly displayed on the statistical distribution map of the age of related tectonic-thermal events (Figure 1-8).
The westward movement occurred in 3000～2900ma, which had different degrees of influence on many areas in North China, such as Jidong, Liaoxi, Liaodong, Jilin, Wutai, Jining and Jiaodong. The westward movement resulted in regional metamorphism and complex plastic rheology of granulite-amphibolite facies in Qianxi Group, Miyun Group, Jining Group, Sanggan Group, Xia 'anshan Group, Longgang Group, Taishan Group, Jianping Group and Jiaodong Group, accompanied by the intrusion of perilla granite, granite and basic-ultrabasic magma. Perilla granite in Yuhuzhai, Taipingzhai and Shangying in western Hebei, Juntunshan gneiss granite in Qian 'an (2960Ma) (Liu Dunyi, 199 1) and Gongchangling granite in eastern Liaoning (3000~2900Ma) (Liu Dunyi,19960) were formed.
Figure 1-8 Statistical distribution map of tectonic-thermal events during the formation of Yanshan (a) and Huashan (b) cratons.
Figure 1-8 Isotopic Age Statistics of Yanshan and Northern Margin of North China Craton during the Formation of Craton Basement
Statistical data include Rb-Sr isochron age, Sm-Nd isochron age, zircon U-Pb age and 39Ar-40Ar age of metamorphic rocks and intrusive rocks.
2. Fuping Movement
Fuping movement occurred in 2600~2400Ma (figure 1-8), which was one of the strongest crustal movements in the early Precambrian of China-Korea platform. Fuping Group and Longquanguan Group in Wutai Mountain area of Shanxi Province were in angular unconformity contact with the overlying Wutai Group, making Dantazi Group, Wulashan Group, Fuping Group, Shang 'anshan Group, Middle-Upper Jianping Group, Middle-Upper Jiaodong Group and so on. Accompanied by intense gneiss dome uplift, solid plastic rheology, ductile shear deformation, gneiss, schist and other extensive structural deformations, as well as intense migmatization and magmatic intrusion, oval structures (dome structures) in Qian 'an, Qianxi, Anshan, Qingyuan and Haicheng, and Shanhaiguan-Suizhong mixed granite belt (2403~2475Ma) and Qidashan granite in Liaodong were formed. 1992), Wulashan granite (2370~2470Ma) (Ma Xingyuan et al., 1990) and granite-greenstone belts in eastern Hebei, northern Hebei, northern Liaoning, Jiaodong, Wutai, southern Jilin, Jiapigou and Wulashan (Shen Baofeng et al., 6544
3. Wutai Movement
Wutai movement roughly corresponds to Shuangshanzi movement in eastern Hebei, which occurred in 2200～2000ma, resulting in angular unconformity and contact relationship between Wutai Mountain Group and the overlying Hutuo Group, resulting in extensive regional metamorphism of high greenschist facies-amphibolite facies of Wutai Group, Shuangshanzi Group, Hongqi Yingzi Group, Setengshan Group, Lower Liaohe Group and Ji 'an Group, accompanied by ductile shear and closed fold. A large number of ductile shear zones, various types of fold structures and Dushan granite (2000Ma) (Zhao Dunmin, 1990), Zhangjiagou diabase porphyrite (2265Ma) (Sunjiashu, 1994) and other magmatic intrusions have been formed. In western Inner Mongolia and Wutai Mountain, some granite-greenstone belts have been formed.
4. Lvliang Movement
The Lvliang movement occurred in 1900 ~ 1800 Ma, which was another most important crustal movement in the early Precambrian of China-Korea platform (Li Junsheng,1939; Ren Jishun et al.,1980; , Cui, 1980), formed a regional fold curtain in Zhuzhangzi-Shuangshanzi, Wutai Mountain, Taihang Mountain, Jin 'an, Jiaodong and other areas in eastern Hebei, which caused strong structural deformation of Zhuzhangzi Group, Hutuo Group, Fenzishan Group, Shangliao Group, Gantaohe Group, Erdaowa Group and Laoling Group with greenschist facies. Zhuzhangzi granite greenstone belt (Li Jinrong, 1997) is formed by the intrusion of granite magma such as Siziwangqi granite, Lan Ying granite (1790Ma) and Banbishan granite porphyry (1757Ma). The unified crystalline basement of China-Korea platform was finally formed in Lvliang period.
The above four crustal movements and tectonic-thermal events were superimposed and reconstructed, forming a rather complicated regional tectonic framework (Figure 1-9).
2. Crustal movement and related tectonic-thermal events during the formation of Neoproterozoic-Paleozoic craton cover.
After the Lvliang Movement, the platform of China and Korea, including Yanshan area, entered a relatively stable development period of craton sedimentary cover until the end of Paleozoic. During this period, the crustal movement was dominated by block ups and downs (land-making movement), forming a multi-stage sedimentary discontinuity and regional parallel unconformity contact relationship; Mesoproterozoic was accompanied by intense rifting, submarine volcanic eruption and synsedimentary fault activities, and regional shallow metamorphism also developed in some areas.
From Mesoproterozoic to early Neoproterozoic (1800 ~ 1000 Ma), the crustal differential movement of North China block is still relatively strong, and it is in the evolution stage of aulacogen (aulacogen and ancient rift valley), forming multiple rift centers (figure 1- 10). Yinshan and Yanshan aulacogen are nearly east-west, mainly composed of nearly 10,000-meter-thick coastal and shallow-sea clastic rocks-carbonate rocks-argillaceous rocks, and there are many layers of submarine intermediate-basic volcanic rocks. Typical Mesoproterozoic pillow lava is still developed in Tieling area of northeast Liaoning. Based on the Datong-Guyuan fault and the Tanlu fault, the aulacogen system is divided into three sections from west to east, namely, the Langshan-Baiyunebo aulacogen in the west, the Yanshan-Liaoxi aulacogen in the middle and the Panhe aulacogen in the east. These gullies are all developed on the basis of ancient craton, and their strata and sediments are comparable to some extent, but their distribution characteristics and structural types are different in their respective development periods and spaces.
The Yinshan trough system in the western section includes Langshan-Baiyunebo and Zhaertai trough, which is linearly distributed in the east-west direction, with a length of more than 500 km from east to west and a width of about 100km from north to south, and its two sides are controlled by nearly east-west synsedimentary faults. The era of aulacogen may be earlier than that of aulacogen, Liao Yan. The Bayan Obo-Aola Trough in the north is deposited in the Bayan Obo Group, with a thickness of 9000m, and is composed of iron rare earth elements, carbonate rocks and intermediate-basic igneous rocks of Jianshan Formation. In the south of Zhaertai Aola Trough, the iron-bearing carbonate-clastic rock formation of Zhaertai Group is deposited with a thickness of 3,200m, and the Ji Shu Formation is sandwiched with alkaline intermediate-basic volcanic rocks (Wang Zhen et al., 1989). Their sedimentary environment is mainly coastal-shallow sea facies, and some areas are semi-deep sea paleoenvironment, forming many clastic-carbonate-argillaceous sedimentary cycles. After the formation of Zhaertai Group and Baiyunebo Group, they experienced strong crustal movement (Zhaertai movement), which caused shallow metamorphism, fold deformation and ductile shear deformation in greenschist facies. The age of this crustal movement is about 65438±0400ma. After 1400Ma, the coastal clastic rock-carbonate rock-argillaceous rock series of Shinagan Group was formed, with a small and constant thickness, which was covered by angular unconformity on the strata in the low valley period, belonging to a typical stable caprock deposit.
Figure 1-9 Archean-Proterozoic paleostructural map of the northern margin of North China block and its adjacent areas (slightly supplemented and modified according to Cui et al. (1980))
Figure 1-9 Archean-Proterozoic paleotectonic map of the northern margin of North China Craton
1 ~ 2— Proterozoic: anticline and inversion anticline, syncline and inversion syncline; 3 ~ 4— Archaean: anticline and inversion anticline, syncline and inversion syncline; 5-Paleoproterozoic: foliation and foliation; 6-Archaean: schistosity and schistosity; 7- Late faults and concealed faults; 8— Paleoproterozoic: intermediate-acid intrusive rocks; 9— Archean: intermediate-acid intrusive rocks; 10- greenstone belt; 1 1— Paleoproterozoic: carbonate rocks; 12 —— post-yanliao movement (1000Ma) molasse formation; 13-the dividing line between Archean and Proterozoic rock series; 14- positive magnetic anomaly; 15- negative magnetic anomaly; 16- oval structure; 17- ductile shear zone; 18 —— magnetic anomaly line of the Tan-Lu fault zone
Map 1- 10 Mesoproterozoic paleotectonic map of the northern margin of North China block (slightly supplemented and modified according to Cui et al. (1976))
Figure 1- 10 Mesoproterozoic paleotectonic map of the northern margin of the North China Craton
1- uplift zone; 2- synsedimentary fault zone; 3— Isothickness line of Mesoproterozoic strata; Yinshan area: Baiyun Obo Group and Zhaertaishan Group; Yanshan and Fanhe areas: Great Wall Group, Jixian Group and Qingbaikou Group; Ji Dan area: Qingbaikou Group and Sinian System; 4- submarine intermediate-basic volcanic rocks; 5- intermediate acid intrusive rocks; 6- basic intrusive rocks; 7- Phanerozoic fault; 8 —— post-Yan-Liao movement (1000Ma) molasse construction; 9— Measuring point of formation thickness
The Liaoyan trough in the middle section is generally distributed in the northeast direction, which is obviously controlled by the Zhangjiakou-Chengde-Beipiao synsedimentary fault. Among them, the Neoproterozoic sedimentary strata are 10,000 meters thick, and the rift center is in Jixian-Chaoyang area, with thick sediments in the north and gradually thinning from south to west. The sedimentary strata are Great Wall Group and Jixian Group from bottom to top, belonging to a set of coastal and shallow sea sedimentary formations, forming the alkaline and intermediate-basic submarine volcanic rock series of Dahongyu Formation in the early Mesoproterozoic. The center of the rift valley is surrounded by uplift belts, most of which are underwater uplift. The rift began at 1800Ma, during which several ascending movements occurred. For example, Luanxian Movement occurred at 1400Ma, which caused the sedimentary discontinuity and parallel unconformity between Jixian Group and Great Wall Group. The Qin-Yu movement of 1000Ma caused the sedimentary discontinuity and parallel unconformity between Qingbaikou Group and Jixian Group. After the Neoproterozoic Xiamaling Formation was deposited, the large-area overlap of glauconite Shi Ying sandstone formation in Jingeryu Formation marked the beginning of the transition to the stable craton caprock development stage.
Dongfanhe Gully Trough is located in the east of the Tanlu fault, and its rifting started later than that of Liao Yan Gully Trough, lacking the Changzhougou, Chuanlinggou and Tuanshanzi periods of the Great Wall period, and the rifting deposition began in Dahongyu period of the Great Wall period. Dahongyu Formation, Gaoyuzhuang Formation and Jixian Formation of Great Wall Group formed in rift period are a set of clastic-carbonate rock series, and their sedimentary characteristics and stratigraphic age are very consistent with those of Yanshan aulacogen, but there are some differences. For example, the pillow-shaped intermediate-basic lava developed in the Wumishan period of the Fanhe Gully, reflecting the great activities of that period. The end time of the Fanhe 'ao Trough is the end of Mesoproterozoic, and the coarse clastic rocks of the Yintun Formation were formed after the Yanliao Movement (1000Ma), and their lithologic characteristics are similar to those of the post-orogenic Molashi Formation.
The eastern part of Jiaodong, the southern part of Liaodong and the southern part of Jinan were all in a state of uplift and denudation during the 800 Ma period of Mesoproterozoic (1800 ~1000 Ma). After the Yan-Liao Movement in the early Neoproterozoic, the molasse formation of Yongning Group and the craton caprocks of Xihe Group, Wuxing Mountain Group and Jinxian Group were formed in Dalian-Fuxian area. In Hunjiang area, southern Jilin Province, the cover deposits of the Molashi Formation of Baifangzi Formation, Xihe Formation and Hunjiang Formation were formed. The sedimentary formations in the above stages have good similarity, and they are mainly composed of stable coastal facies and shallow marine facies, with clastic-carbonate-argillaceous sedimentary cycles. Affected by the crustal movement in the early Mesozoic, this stratum experienced regional shallow metamorphism, such as Xihe Group in Lvda area and Penglai Group in Jiaodong.
Comparing the three Mesoproterozoic aulacorns in the east, middle and west, we can see that they are comparable in many aspects, but there are also great differences.
From Neoproterozoic to late Paleozoic, the tectonic activity of China-Korea platform was further weakened and the crustal tectonic movement was weak. Most of the time (CAMBRIAN-Middle Ordovician and Middle Carboniferous-Permian), the whole area was in a stable coastal and shallow marine sedimentary environment, during which sea level fluctuated many times. From the late Ordovician to the early Carboniferous, a land-building movement characterized by overall uplift occurred, resulting in long-term sedimentary discontinuity and regional parallel unconformity. During this period, there was no strong tectonic thermal event.
3. Crustal movement and related tectonic-thermal events during Mesozoic-Cenozoic intracontinental orogeny.
Yanshan and its adjacent areas entered a new period of Mesozoic-Cenozoic tectonic activity, that is, intracontinental orogeny, after a long period of development from Mesoproterozoic to Paleozoic sedimentary caprocks. Indosinian movement and Yanshan movement have had a strong influence not only on Yanshan area, but also on the vast area of East Asia, and they are one of the most important crustal movements in geological history. Mesozoic-Cenozoic tectonic movement in Yanshan and its adjacent areas and its related deformation, inversion structure and magmatic activity are often reflected in episodic events.
Through long-term geological investigation and research, 5 ~ 6 Mesozoic regional angle unconformities have been identified in Yanshan and its adjacent areas, and each regional angle unconformity represents a folding curtain or orogenic curtain (Cui He,1983; Cui et al.,1985; Cui et al.,1990; Cui He,1997; Cui et al., 1998) (tables 1-2 and 1-4). There were 12 tectonic episodes in Indosinian of Yanshan orogenic belt, including "Qianxingshikou Formation" at the end of Middle Triassic and "Qiannandaling Formation" at the end of Late Triassic, which marked the beginning of Mesozoic intracontinental orogeny in this area. There are four regional tectonic episodes in Yanshan period (Jurassic-Cretaceous), including Qianlijishan Formation and Qiandonglingtai Formation (Qianyixian Formation) in the early Yanshan period, and the tectonic episode between Qiansunjiawan Formation and Upper Cretaceous and Lower Tertiary in the late Yanshan period. The main geological events related to the above 5-6 tectonic or orogenic episodes include the formation of Mola-like formations in the same orogenic period and magmatic intrusions of different natures, fold changes and thrust fault activities related to intense compression, magmatic eruption events in the post-orogenic period, the appearance of several new sedimentary basins or volcanic-sedimentary basins related to slow extension, and the activities of syndepositional fold and synsedimentary fault.
Table 1-4 Summary of Mesozoic volcanic sedimentary structures and regional angular unconformity development periods in Yanshan orogenic belt
Figure 1- 1 1 Schematic diagram of Mesozoic structure-structure distribution of Yanshan intracontinental orogenic belt
Figure 1- 1 1 Mesozoic tectonic map of Yanshan intracontinental orogenic belt
1- Archean-Proterozoic structural layer; 2- Mesoproterozoic-Paleozoic structural layer; 3-6 Mesozoic volcanic-sedimentary formation: 3- glutenite series, 4- coal-bearing series and oil shale series, 5- acidic-intermediate-acidic volcanic-sedimentary series, 6- basic-neutral volcanic-sedimentary series; 7- Mesozoic regional thrust nappe fault structural belt; 8- granite; 9— Alkaline granite; 10- neutral intrusive rocks; 11-alkaline rocks; 12- basic intrusive rocks; 13-Angle unconformity; 14- Hidden and Inferred Geological Boundary
The Mesozoic multi-stage and multi-episode crustal movement and the superposition of tectonic-thermal events formed a rather complex regional tectonic framework of Yanshan intracontinental orogenic belt (Figure1-1).
The Cenozoic development of Yanshan orogenic belt is incomplete and its distribution is limited, so it is difficult to directly observe the obvious angular unconformity interface. In the Lower Liaohe River and North China Rift Basin in the southeastern margin of Yanshan orogenic belt, there is a wide range of angular unconformity between sediments in the Early Tertiary fault depression and the Late Tertiary-Quaternary depression (Li Guoyu et al., 1988). It is estimated that this episodic event, which occurred between the early and late Himalayan period, should also have some influence on the Yanshan orogenic belt. In addition, with the uncoordinated uplift of Yanshan Mountains in Himalayan period, there were two planation planes (199 1) at different altitudes in Beitai period (early Paleogene) and Tangxian period (late Miocene).