In the basement rock systems on the north and south sides of the Qinling-Dabie orogenic belt, there are two regional fault systems, namely NWW to near EW that have been developed for a long time since the early Paleozoic and have obvious inherited activities. The NE-NNE trending fault system and the late (Mesozoic and Cenozoic) developed NE-NNE trending fault system. The inherited development of these two regional fault systems controls the formation and evolution of the caprock structural system and its constituent units in South and North China. Together with the basement rock series and its various structural components, they constitute the structural system in the basement rock series of the study area.

Figure 2-6 Relationship between Mesozoic and Cenozoic basin distribution and regional structure in southern North China

(Modified after Xu Hanlin et al., 2003b)

F1—Luan Sichuan-Gushi-Feizhong fault; F2-Tancheng-Lujiang fault; F3-Jiaozuo-Shangqiu fault; F4-Xiayi-Woyang-Macheng fault; F5-Shangshui-Chenqiu fault; F6-Zhuanlou-Huaiyang Fault; F7-Yexian-Lushan-Huainan fault; F8-Xiangcheng-Jiaxian fault; F9 Jiyuan-Gongxian fault; F10-Wuzhiling fault; F1-1 Qingyangkou fault; F12-Wuzhi fault; F13- Zhongmu fault; F14-Liaocheng-Lankao fault; F15-Fushan fault; F16-Ningling-Caoxian fault; F17-Shanxian fault; F18-Fengpei fault; F19-Subei fault; F20-Banqiao fault; F21-Wu He Fault; F22-Shangtangji Fault; F23-Yingshang Fault; F24-Taihe Fault; F25-Songgou-Huainan Fault; F26-Bozhou-Jieshou-Guangshan Fault

1.NWW— Nearly EW trending fault system

This fault system is bounded by the Qinling-Dabie orogenic belt and is divided into two parts, the north and the south. The trend of this fault system is consistent with the direction of the Qinling-Dabie orogenic belt. It spreads out in a roughly broom-like shape from west to east on the plane. It is nearly EW-trending to the west of Danfeng, Shaanxi Province. It is mainly NW-trending in Henan Province, and gradually moves toward the east. Spread north and south (Figure 2-7). Its origin may be closely related to the multi-stage merger of the Yangtze Plate and the North China Plate, as well as the formation and evolution of the Qinling-Dabie orogenic belt.

Figure 2-7 Regional structure and fault system in the southwest of southern North China

(According to Yang Weiran, 1987, supplemented)

1—Xixia Basin; 2—Post-Archaean orogenic belt; 3—Archaean terrane; ① Yiyang-Linru-Luohe deep fault; ② Luonan-Queshan-Hefei deep fault; ③Shangxian-Tongbai-Shucheng deep fault; ④ Danfeng-Xixia-Yingshan deep fault; ⑤ Shanyang-Suizhou deep fault; ⑥ Zhen'an-Xichuan-Junxian deep fault; ⑦ Baihe-Xiangfan-Guangji deep fault; ⑧Jiaozuo-Shangqiu fault

< p>(1) NWW-EW trending fault system on the northern side of the Qinling-Dabie orogenic belt

The northern part of this fault system is developed in the fault-fold belt on the southern margin of North China and the North Qinling-North Huaiyang structural belt. The main components include those shown in Figure 2-7: ① Yiyang-Linru-Luohe deep fault; ② Luonan-Queshan-Hefei deep fault; ③Shangxian-Tongbai-Tongcheng deep fault. These faults have the distinctive characteristics of long-term development and strong inherited activity, and have obvious control over the development of the Mesozoic and Cenozoic basins in the southern part of the study area. Among them, the Shangxian-Tongbai-Tongcheng deep fault is the southern boundary of the study area. In addition, there is an important dividing fault in the northern part of the study area - the Jiaozuo-Shangqiu fault (F3 in Figure 2-6), which is also a basement fault that has experienced multiple tectonic activities and has strike-slip properties.

The Yiyang-Linru-Luohe Deep Fault, also known as the Sanmenxia-Lushan-Wuyang-Fuyang-Huainan Fault, is the rough boundary between the stable area of ??the North China Plate and its southern edge tectonic belt (Figure 2-7 ①). This is a large fault with an S or SW tendency, steep top and gentle bottom, intermittently active, and cuts into the deep crust. The different modes of activity in different periods determine the geological differences on both sides of the fault (Figure 2-8). The fault appears as a bead-like anomaly on the aeromagnetic map, and the ΔT planar polar magnetic field appears as a linear anomaly zone and a gradient zone. On the 5km map extending upward from the polarization pole, this zone is the dividing line of different anomalies and a negative anomaly zone. Extending 10km upward is the negative magnetic anomaly zone and zero value line. Gravity anomalies are characterized by linear gradient zones. It can be seen that the fault is a deep fault zone. According to the forward calculation results of the aeromagnetic ΔT curve, the tendency of the fracture section is SSW. On the aeromagnetic map extending 10 to 20 km above the polarization pole, this fault divides the southern part of North China into two different regional magnetic fields in the north and south, forming the above-mentioned Neoarchean Taihua Group advanced schist area and the Neoproterozoic Dengfeng Group granite- Boundaries of greenstone areas. It may have been formed earlier and is the main thrust fault at the front of the thrust body formed by the northward thrust of the Qinling-Dabie orogenic belt in the Indosinian period. In addition to the continued thrusting from south to north in the Yanshanian period, right-side thrust faults also occurred. The cyclonic strike-slip activity thus controlled the Tanzhuang-Chenqiu Early Cretaceous strike-slip pull-apart basin and the Yanshanian intermediate acid magma intrusion and eruption produced along the fault zone. This fault is generally consistent with the Cenozoic Xinqiao Fault (Yelu Fault) at the southern edge of the Tanzhuang Sag, which is the result of the reversal of the fault in the Paleogene. On the 324 seismic line (Figure 2-9), the lower part of the fault shows that the Carboniferous-Permian thrust is above the Lower Cretaceous, while the upper part shows a normal fault with significant Cenozoic inversion characteristics. This phenomenon indicates that there has been a major shift in the tectonic stress field.

Figure 2-8 Qingcaoling thrust nappe structure in Hanliang Coalfield, Lushan, Henan

(According to Shi Quanzeng et al., 1988)

1—Archaean; 2—sandstone; 3—limestone; 4—shale; 5—carbonaceous mudstone; 6—dolomite; 7—clastic limestone; 8—Middle Proterozoic Majiahe Formation; 9—Lower Permian Shanxi Formation

Figure 2-9 Seismic interpretation section at the southern edge of Tanzhuang Sag

Surveying line 324 shows that the Carboniferous-Permian thrust on the Lower Cretaceous

Luo The Nan-Queshan-Hefei Deep Fault, also known as the Luanchuan-Queshan-Gushi Fault, runs NWW and terminates at the Tanlu Fault. It is 550km long and cuts downward to the ancient basement. It is the link between the North China Plate and the Qinling-Dabie Plate. The dividing fault at the northern edge of the orogenic belt (② in Figure 2-7). To the north of this fault is the stable sedimentary area on the southern edge of the North China Plate, and to the south is the North Qinling sedimentary area. There are great differences in stratigraphic sequences, paleontology, sedimentary lithofacies and construction, as well as metamorphism and structural characteristics on both sides of the fault. The aeromagnetic anomaly map shows that there are gentle positive and negative magnetic anomalies to the north of the fault, and a NWW-trending beaded alternating positive and negative anomaly area to the south (Henan Provincial Bureau of Geology and Mineral Resources, 1989). Various phases of magmatic activity develop abnormally near the fault zone. Within and on both sides of the fault zone are Paleoproterozoic mixed granite, mid-Neoproterozoic thick volcanic rock series, early Paleozoic acid intrusive rocks, Mesozoic granite and medium-acid intrusive rocks, etc., indicating that they are deep and large faults that have been active for a long time. In the Proterozoic to Early Paleozoic, it is speculated that this fault was a south-dipping normal fault, which was the boundary between stable North China craton sedimentation and North Qinling rift-passive continental margin sedimentation. By the late Paleozoic, it became the rough boundary between the North China-type craton-type stable sedimentation and the North Qinling-North Huaiyang foreland-type sedimentation. During the Indosinian-Yanshan period, large-scale northward thrusting occurred, accompanied by dextral strike-slip.

Shangxian-Tongbai-Shangcheng Deep Fault The Shangxian-Tongbai-Shangcheng Deep Fault is also called the Shangdan Fault Zone (③ in Figure 2-7), which extends along the southern edge of the North Qinling Mountains and the northern edge of the Dabie Mountains Thousands of kilometers long, it is the plate subduction and collision suture zone during the main orogenic period of the Qinling Mountains

Zhang Guowei, Liu Shaofeng, Cheng Shunyou. 1997. Research report on the Qinling-Yangtze-South China oil and gas geophysical comprehensive interpretation section. Two types of ophiolites and volcanic rocks with different properties remain in this zone: the Neoproterozoic and the Paleozoic. The Neoproterozoic is a small ocean basin type, and the Paleozoic is a multi-island arc type. Linear-collision type granites are developed in the zone. (323～211Ma; U-Pb, Rb-Sr), while on its north side, two phases of subduction-type granite [(793+32) Ma to 659Ma, 487～382Ma; U-Pb, Rb-Sr] are distributed in a belt. The geochemical polarity from south to north shows the effect of northward subduction and collision; between its north side and the Luonan-Queshan-Hefei deep fault, there is a tectonic magmatic complex in the middle and late Early Paleozoic Era (500-400 Ma). The rock belts, including the Danfeng Group volcanic complex belt, the Yunjiashan-Erlangping volcanic complex belt, and the island arc basic and calc-alkaline magmatic complex belt (Zhou Dingwu et al., 1995), represent the active continental margin extrusion type. Tectonic-magmatic environment; Carboniferous-Permian forearc deposits are also intermittently distributed in this zone. Among them, the Xinyang-Shangcheng line has deposited more than 7000m thick basin-facies flysch formations and marine-continental alternating facies coal-bearing formations; The belt is currently based on faults or ductile zones (211-126 Ma; U-Pb, Sm-Nd) of different ages, properties, and structural levels as the skeleton, containing and mixing many of the above types and sources of rock blocks, forming a multi-stage composite Structural melange zone. This fault zone has been the dividing line between the Yangtze Plate and the North China Plate since the end of the Neoproterozoic, and later became the junction zone between the Qinling Mountains and the North China Plate. All this shows that there once was a Phanerozoic limited ocean that disappeared in this zone

Zhang Guowei, Liu Shaofeng, Cheng Shunyou. 1997. Research report on the Qinling-Yangtze-South China oil and gas geophysical comprehensive interpretation section.

Jiaozuo-Shangqiu Fault This fault is located in the Jiyuan, Jiaozuo, Lankao, and Shangqiu areas. It runs nearly EW and is more than 400 kilometers long. The fault distance is as high as 1000-6000m. It extends longitudinally to the Archaean Universe. It is one of two types of faults. The watershed structured in different directions is also the northern boundary of the southern region of North China. The fault surface tilts southward in most areas with a large dip angle, and steeply tilts northward in some areas. The trend of the structural line north of the fault is NNE or nearly SN, while the trend of the structural line south of the fault is nearly EW or NW W. The western section of the fault (west of Jiaozuo) is exposed on the surface, forming the boundary between the mountainous area and the basin. The relative height difference ranges from a few hundred meters to nearly a kilometer. Along the fault, there are dynamic metamorphic rock zones tens to hundreds of meters wide, including Neoproterozoic metadiabase and diorite. Himalayan basalt, andesite and acidic volcanic rocks are distributed in the Fengqiu and Lankao areas, and Yanshan period granodiorite and gabbro are developed in the Yangshan area in the east, indicating that the fault formed early, cut deeply, and is a deep fault with long-term activity. The fault appears as an intermittent step belt on the Bouguer gravity anomaly map, while it appears as a steep step zone in the Yanjin, Shangqiu, Yucheng, and Xiayi areas, indicating that the rock density difference on both sides of the fault in the above-mentioned areas is relatively large. The side is the ascending plate, which is composed of the Lower Paleozoic, and the northern plate is the descending plate, which is composed of the Paleogene with a thickness of more than 3000m. On the aeromagnetic anomaly map, a stepped magnetic anomaly zone appears between Minquan and Shangqiu, forming the dividing line between positive and negative magnetic fields, indicating that the basement of the Archaean universe has undergone significant displacement.

To the west of Shangqiu, it rises in the north and falls in the south, while near Shangqiu, it rises in the south and falls in the north, reflecting that this fault is a basement fault that has experienced multiple tectonic activities and has strike-slip properties.

(2) NWW-EW trending fault system on the southern side of the Qinling-Dabie orogenic belt

The southern part of this fault system is developed in the Suizhou-Tongbai-Dabie block (Fig. 2-7), the main components include: ④ Danfeng-Xixia-Yingshan deep fault in Figure 2-7; ⑤ Shanyang-Suizhou deep fault; ⑥ Zhenan-Xichuan-Junxian deep fault; ⑦ Baihe-Xiangfan -Guangji Deep Fault. The four deep faults mentioned above in Figure 2-7 mainly control the orogenic uplift and intermountain rifts within the orogenic belt. Among them, the Baihe-Xiangfan-Guangji deep fault is the boundary fault between the orogenic belt and the Yangtze stable block; the next three deep faults extend southeastward to Hubei and Anhui, and then converge in the Jiujiang area. It can be seen from field outcrops and satellite photos that these NW-NW W-trending fault systems are usually intercepted and displaced by NE-NNE trending fault systems. Since these faults are mostly distributed outside the study area, they will not be described again.

2. NNE-NE trending fault system

The late NE-N NE trending fault in the study area is roughly parallel to the Tanlu fault (F2) (Figure 2-6), except The larger ones outside the Tanlu fault zone are the Songgou-Huainan fault (F25), Xiayi-Woyang-Macheng fault zone (F4), Bozhou-Jieshou-Guangshan fault (F26), and Liaocheng-Lankao fault (F14) , Ningling-Caoxian fault (F16) and Qingyangkou fault (F11).

These faults tend to gradually shift from NNE to NE from east to west, except for the Tanlu fault zone (F2), the Xiayi-Woyang-Macheng fault zone (F4) and the Bozhou-Jieshou fault zone. -Except for the Guangshan fault (F26), the scale is smaller than that of the nearly EW-NWW faults, and they appear intermittently. Among them, the Xiayi-Woyang-Macheng fault located in the central part of the area is composed of three discontinuous strike-slip faults arranged in a right-moving echelon pattern. Between Shangcheng and Macheng, the northern section of the fault is inclined to NWW, while the southern section is inclined to SEE, with an inclination angle of about 70°. This reflects from one side that the fault has the nature of a strike-slip fault. Mylonite, fault breccia and cataclastic rocks developed along the fault zone. The 40Ar-39Ar isotope isochron age of the biotite single mineral in the mylonite is (226.6+12.6) Ma (Wang Yitian et al., 2000), which belongs to Products of the Indosinian period. The formation of these structural rocks is related to the thrust-nappe structure from south to north within the Qinling-Dabie orogenic belt. This fault should be a thrust fault formed basically at the same time as the thrust body or slightly later than the thrust body. It is a line formed in the NS compressive stress field that is almost perpendicular to the thrust nappe structure and perpendicular to the direction of the orogenic belt. Lateral strike-slip faults.

Data show that the Xiayi-Woyang-Macheng fault was formed in the late collision period between the Yangtze Plate and the North China Plate. It was very active after its formation and not only controlled the late collision and exhumation process of the two major plates. Moreover, under the adjustment of lateral strike-slip conversion, the southern part of the fault resulted in the differential uplift and subsidence of the blocks on both sides of the fault (the Hong'an block and the Dabie block) and the relative rotation of the two, thus affecting the Dabie orogeny. The structural pattern of the belt. Today, seismic activity along the Xiayi-Woyang-Macheng fault also occurs from time to time (Hubei Provincial Bureau of Geology and Mineral Resources, 1990). This shows that the Xiayi-Woyang-Macheng fault has long-term activity and is a strong tectonic stress concentration zone, which is of great significance in the evolution of the Qinling-Dabie orogenic belt and southern North China.

It is these NNE-NE and EW-NWW trending faults and the basement pre-existing fault network that controlled the Cretaceous-Paleogene rift basins, such as Sanmenxia, ??Luoyang, Luyi, The formation and evolution of Banqiao and Xinqiao caused the Mesozoic and Cenozoic tectonic systems in the study area to have an east-west branching and north-south blocking pattern as mentioned above. These small Mesozoic and Cenozoic rift basins were all bounded by NW-trending faults and NE-trending faults in the early stage, and were characterized by small scale and scattered development. It was not until the Neogene that they developed into unified NNE-trending large-scale depressions. Their formation and evolution may be controlled by the regional tension after the uplift period of the Qinling-Dabie orogen on the one hand, and the creeping effect during the exhumation of the converged subducted lithosphere on the other hand.

3. Tectonic framework of basement rock series

The basement structure, form and properties in southern North China are relatively complex, and there are basement structures and structural characteristics of different basins (depressions). significant difference. This difference is manifested in the difference in anomaly shape and value on the regional aeromagnetic anomaly map - the aeromagnetic anomalies also have the characteristics of north-south zoning and east-west zoning on the plane. For example, the Kaifeng Depression in the north has a basement of Precambrian metamorphic rock series, including the Archaean and Paleoproterozoic, which is magnetic. Among them, Chengwu and Yutai are located in the positive anomaly area, and the basement is inferred to be the Archaean; Jiyuan, Kaifeng, Minquan, and Huangkou are located in the negative anomaly area, and the basement is inferred to be the Paleoproterozoic (Figure 2-10). According to the analysis of geological and geophysical data, there are three types of lithofacies in the Precambrian basement of the area (Figure 2-11): ① The first type is the Paleo-Middle Archaean rigid rock with strong magnetism, which is pyroxene-hornblende Granulite phase; ② The second type, Paleo-Neoarchean rigid rock with medium magnetism, belonging to the amphibolite gneiss phase; ③ The third type, Neoarchaean-Paleoproterozoic soft rock with weak magnetism The rock mass belongs to migmatite and medium-light metamorphic lithofacies.

< /p>

Figure 2-11 Precambrian basement lithofacies structure diagram of the Kaifeng Depression and adjacent areas

1) Single-layer basement: mainly the first or second type of basement lithofacies As well as the basement composed of the combination of the two, the rocks of this type of basement are older and belong to the Archaean universe, with a deeper degree of metamorphism and stronger rigidity.

2) Double-layer basement: It is composed of the third type of basement lithofacies and the first and second types of basement lithofacies. Its main feature is the development of Paleoproterozoic middle layers with different thicknesses. —A shallow metamorphic rock system, and there may be Archaean Universe beneath it, forming a double-layered structure. This type of basement is less rigid than a single-layer basement because the Paleoproterozoic is relatively soft.

Existing data show that in the Zhongmu Sag, Minquan Sag and Huangkou Sag in the northern part of the study area, the basement is mainly composed of the second and third types of basement lithofacies, and is dominated by double-layer basement; Jiyuan Sag, Chengwu Sag and Yutai Sag are mainly composed of single-layer basement and are composed of the first and second types of basement lithofacies. In the Zhoukou Depression in the central part of the study area, the basement (rock) is the ancient Archaean-Paleoproterozoic crystalline rock of the North China Block. In the Hefei Depression in the southern part of the study area, the basement (rock) is composed of Proterozoic-Archaean metamorphic rock series, and the magnetic anomalies caused are distributed in nearly EW-directed strips along the fault trend. It is roughly bounded by the Feizhong Fault, and to the north is the North China continental crust type metamorphic crystalline basement. The Neoproterozoic-Paleozoic is dominated by stable platform type (platform-shelf phase) sediments; to the south it gradually becomes the North China passive continental margin. Transitional shell crystalline basement, Neoproterozoic-Paleozoic mainly slope-basin facies sediments. In the Xinyang Depression on the west side of the Hefei Depression, the basement rock series is the Proterozoic Yuqinling Group and the Lower Paleozoic Devonian Waimiao Formation (Henan Provincial Bureau of Geology and Mineral Resources, 1989).