The so-called geological structure refers to the deformation and displacement of the strata and rock mass that make up the crust under the internal and external dynamic geological action, thus forming geometric bodies or traces left by the deformation and displacement of the strata and rock mass that make up the crust under the internal and external geological action (mostly tectonic movement), such as folds, joints, faults, cleavage and other planar and linear structures.
principle
The in-situ stress field of repeated orogeny has formed three structural types under the changeable in-situ stress conditions, which are intertwined into complex and changeable strain images.
Characterized in that:
(1) Geological structure belongs to intraplate structure, and the main structure is thin-skinned structure.
(2) The deformation is not very strong, and the most complete and extensive structural style in Guizhou is the Jura Mountain Fold Belt.
Duyun Movement: named by the Eighth General Survey Brigade of the former Ministry of Geology and Mineral Resources (1980), it refers to a crustal movement in central and southern Guizhou between the end of Ordovician and the beginning of Silurian.
The performance of this movement is:
In central Guizhou between Bijie-Zunyi-Meitan-Tongren line and Guiyang-Shibing line, there is a general lack of false integration of upper middle Ordovician, upper middle SILURIAN and lower Ordovician. In many areas, such as Wudang, Guiyang, it can be seen that the conglomerate layer or gravelly clayey clay rock at the bottom of Silurian system is embedded in the discontinuous surface with ups and downs of several meters. In southern Guizhou, the middle of Lower Silurian overlaps with different horizons of Ordovician, and the missing horizon is 100 meters. There are ordinary breccia at the bottom of Silurian system and weathering crust in some areas. This is a large-scale ascension movement.
Dushan Uplift: Named after Wang Yue 1994, it refers to the uplift movement between Jiwozhai section and the underlying Songjiaqiao section of the Middle Devonian Dushan Formation in Dushan area. There is a weathered residual limonite layer at the bottom of Jiwozhai section of Dushan Formation in this area, and the bottom conglomerate is above it. In addition, according to the regional comparison of trace fossil assemblages, it can be confirmed that the upper part of Songjiaqiao section of Dushan Formation has been weathered and eroded to varying degrees. The bottom of Jiwozhai section is directly covered on the uneven base. All these indicate that after the deposition of the Songjiaqiao section of Dushan Formation, the crust has undergone an extremely extensive and obvious upward movement.
Guizhou-Guangxi Movement: Zhao et al. named it in (1959), originally referring to the false integration of Qixia Formation and Maping Formation in Guangxi. In Guizhou, except for some areas, Maping Formation and its overlying Liangshan Formation and Qixia Formation are all false integrations, so this name is used. According to the latest geological chronology published in China, this movement occurred between the Middle and Lower Permian.
Movement: Lin (1994) was named. Named Qinglong Bi Hen Camp. There are obvious folds and faults in the early Early Pleistocene strata (such as Pingdi Formation), and the dip angle of strata reaches 50 ~ 70 locally, but the overlying sediments in the middle and late Early Pleistocene are not deformed. Lin called the tectonic movement that deformed the late Cenozoic deposits in the middle and late early Pleistocene and before it movement. According to the analysis of existing data, it happened about 1.50 ~ 1.20 million years ago. It is the strongest tectonic movement in Guizhou in the late Cenozoic, which is roughly equivalent to the Yuanmou movement in Yunnan. This movement began a new period in which the crust of Guizhou tilted from west to east.
Jura-type fold belt: Jura-type fold belt is characterized by different deformation strengths of anticline and syncline, and relatively closed folds and relatively open folds are alternately juxtaposed, representing barrier folds and trough folds. The Jura-type fold belt occupies most of the Yangtze landmass in Guizhou, and the strata involved are from Mesoproterozoic to Mesozoic. Although there are many kinds of fold styles, the trench fold is the most developed and typical. It is composed of a series of tight synclines and gentle anticlines arranged alternately in parallel, which are arranged in a goose shape in plane and section. In a large scale, thrust faults parallel to the fold axis (mainly anticline axis) are generally developed, and together with the above folds, fold-nappe structures are formed. The occurrence of thrust section is generally gentle, and sometimes there are flying peaks or structural windows; Others form double structure or imbricate thrust rocks. In addition, another important fault in the area is a strike-slip (translation) fault that obliquely intersects with the above-mentioned folds and thrust faults, which forms a complex fault network with the above-mentioned thrust faults. In addition, a small-scale tensile structure-dustpan fault, which often appears in the form of a half graben basin, has developed beside some large faults in the Jura-type fold belt, and the accumulated late Cretaceous molasses has been slightly deformed, which is obviously the manifestation of Himalayan movement. Flat and open fold belt on the edge of Sichuan Basin: It belongs to the southern edge of Sichuan Basin, and its scope is limited to Chishui and Xishui cities (counties) in our province. The tectonic deformation in this area is weak, the stratum occurrence is generally flat, some even horizontal, and the folding is extremely slow. From the late Late Triassic to the late Cretaceous, the folds dominated by continental clastic rocks are generally open, and the types are mainly horizontal and thin, with only a few small-scale gentle anticlines and synclines, which are mainly distributed in the east-west direction. The fault structure is not developed, and there are only some small normal faults. According to the deep geophysical data in Sichuan, the basement of the basin is the early Precambrian crystalline basement with high degree of hardening. The above-mentioned structural deformation is obviously a cover fold that stabilizes the upper part of the craton and belongs to the Germanic-like fold in the foreland basin. Nanpanjiang orogenic fold belt: Nanpanjiang area belongs to the southwest section of South China active belt. The strata involved in this belt range from Upper Paleozoic to Mesozoic, among which the terrigenous clastic complex of Middle-Upper Triassic is the most striking. The main tectonic line is NW -NWW, which is a tight fold and thrust. The most widely distributed terrigenous clastic rocks of Middle-Upper Triassic have strong structural deformation. Common continuous linear tight folds, regional plate cleavage development, large recumbent folds, syncline folds, fan-shaped folds, pointed folds and other complex small and medium-sized structures, are also very common and spectacular. It is worth pointing out that the deformation of Triassic in this area is different from the general simple cleavage vertical fold. Due to the complex lithology of this layer, a composite fold pattern has been formed, including concentric and equal-thickness box-shaped non-cleavage and less-cleavage folds, as well as sharp-edged folds with the same cleavage and their transitional types. Refractive cleavage is also accompanied by fold cleavage and plate cleavage; The dip angle of fold twist is also different in different parts, which indicates that the fold in Nanpanjiang area is orogenic, but it has certain particularity. Jiangnan basement fold thrust belt: the southeast of Zhenyuan-Kaili-Sandu line is a part of Xuefeng mountain area, where Precambrian shallow metamorphic rocks are exposed in a large area. Traditionally, this is an ancient land that has existed for a long time since Precambrian, and it is called "Xuefeng ancient land" (that is, the southwest section of Gujiang land). The research shows that from Neoproterozoic to early Paleozoic, "Xuefeng ancient land" did not exist. Caledonian movement folded the area into mountains and welded it with Yangtze landmass. And rose to land (because of this, some geologists regard Xuefeng Mountain as a part of the Jiangnan orogenic belt in Caledonian), but at that time, the area was not a separate ancient land, but a part of the whole upper Yangtze ancient land. Soon the seawater re-entered this area, and it was still under the seawater for most of the late Paleozoic and early Mesozoic, but it surfaced from time to time. The Indosinian movement at the end of Triassic made the Xuefeng area land-based, and ended the marine deposition in this area. The imbricate thrust fault to the northwest in Yanshan period exposed a large area of Precambrian in this area, which has deep deformation characteristics such as basement involvement deformation, extensive cleavage and double thrust structure. The western edge of the belt is a series of arc thrust faults that tend to protrude from southeast to northwest. In Zhou Xi, south of Kaili, Xiajiang Group overthrusts the Permian, covering the southeast wing of the whole syncline. The same front fault saw a Feilai peak composed of Lower Cambrian in Yuping. Similarly, the Ge Dong fault parallel to the former is also covered by the Sansui syncline with the Cambrian as the core. These materials show that the belt has undergone a large-scale horizontal contraction. Field observation shows that imbricate thrust occurred before the late Cretaceous. According to the distribution of sedimentary facies belts in different periods, the comparison with the surrounding areas, and the thrust estimation of the main faults in the front of the uplift belt, Xuefeng uplift is a Huaiyuan body with a displacement distance of less than tens of kilometers. Generally speaking, this belt is an orogenic belt destroyed and reconstructed by imbricate thrust in Yanshan period in Caledonian period. Liupanshui fault basin: refers to a trough-shaped fault basin that spread northward along Weining, Shuicheng, Liuzhi and Zhenning under the influence of Emei ground fissure in the late Paleozoic. Both sides of the basin are controlled by Ziyun-Duya synsedimentary fault and Weining-Shuicheng synsedimentary fault respectively. Devonian, Carboniferous and Middle and Lower Permian in the basin are dark carbonate rocks, mudstone and siliceous rocks deposited in deep water, mainly containing plankton. The corresponding strata on both sides of the basin consist of light-colored carbonate rocks rich in benthic fossils. The late Permian trough basin died out. According to geophysical data, there are concealed volcanic rocks in the trough-basin distribution area along the northwest. The edge of the fault basin not only controls the distribution of Devonian and Carboniferous lead-zinc mines and hydrothermal siderite, but also controls the distribution of NW-trending deformation zone formed in Yanshan period. The NW-trending deformation zone in southwest Guizhou (also known as Shuicheng-Ziyun deformation zone) refers to a large-scale deformation zone extending NW in Weining, Shuicheng, Liuzhi and Zhenning. The belt is about 250 kilometers long and 20 ~ 50 kilometers wide, with a trend of 50 northwest to 50 southeast. It is composed of a series of inverted folds and thrust faults composed of Upper Paleozoic, Triassic and Jurassic, but its combination mode is different in different sections. For example, in Shazigou-Liu Ma section, the thrust direction and thrust direction of the fold are both southwest; In Huangguoshu-Xiaojianjian area, folds and thrust faults form a hedge pattern. It is worth noting that the NW-trending deformation zone is not only characterized by compression, but also by sinistral sliding. Leigongshan transitional shear zone: refers to the brittle-ductile or ductile-brittle strong deformation zone in the middle and deep crust (10- 15km) developed in Taijiang, Leishan and Sandu, which is dominated by shear deformation. According to the research of Zhu Ailin et al. (1998), the transitional shear zone is macroscopically characterized by a series of cleavage dense zones arranged in a parallel echelon from 30 to 50 in the northeast, and there are shear folds, shear lenses, S-C structures, tensile lineation, bedding recumbent folds, rootless folds and sheath folds. Microscopically, it is mainly shear deformation, and the mineral composition changes accordingly, resulting in mylonitized rocks. In addition, the shear zone and surrounding rock are in transition, and there is no obvious boundary between them. The shear zone in this area is mainly developed in sericite, silty slate and tuffaceous slate in greenschist facies. The argillaceous and tuffaceous components of the original rock are heavier, and the mineral particle size is smaller. After strong extrusion and shearing, although there is plastic deformation, there is no obvious grinding thinning. This well-preserved original rock feature, without obvious grain size reduction, appears in a narrow zone with dense cleavage and flow structure, which is called mylonitized rock. According to the relevant test data, the eastern boulder is formed in the transitional shear zone, the formation depth is above 14Km, the temperature is above 350°C, and the confining pressure is between 364 and 390 MPa.