The three major plates, Tarim, China-Korea and Yangtze, and 53 micro-landmasses between Siberia, India and Pacific, all have Precambrian basements. Among them, there are 5 micro-landmasses separated from Siberia plate, 6 micro-landmasses separated from Gondwana continent, and the remaining 42 micro-landmasses belong to China ancient landmasses, of which 38 are in Chinese mainland, accounting for 70% of the micro-landmasses in East Asia (according to Ren Jishun, 1999, with modifications).
The report divides the China part of the Eurasian plate into seven plates: Siberia, Tarim, North China, Yangtze, Cathaysia, Gangdise-India and Philippine. There are four microplates between the plates: Junggar-Ili, Songnen-Jiamusi, Qaidam-Qilian and Qamdo-Gangdise. These ancient plates and micro-plates were collaged in Triassic and became a part of the huge Eurasian plate. The Eurasian plate is adjacent to the Pacific plate, located in the arc trough zone in the east of Japan, and connected with the Philippine Sea plate in the southeast through the Taitung vertical valley junction zone (according to China Geological Survey, 2004).
There are six suture zones between the above seven plates, such as Ilya Bierga-Xilamulun-Jilin-Hunchun junction zone, Altun junction zone, Kangxiwa-Shangnan-Jimo-Mu Ping junction zone, Bangongcuo-Nujiang junction zone, Qinzhou Bay-Hangzhou Bay junction zone (Shaoxing-Pingxiang-Beihai fault zone) and Taitung longitudinal valley junction zone. There are also six plate combination zones at the edge of the four blocks, such as Ejina Banner-Heihe River, South Tianshan Mountain, North Qilian Mountain, Jinsha River-Honghe River, Longmucuo-Lancang River and Yarlung Zangbo River. These combination zones are connected in multiple stages in time, mostly in the east early and in the west late. In space, it is a broadband with reduced, mixed and overlapping structures. Most of the belts are mixed structures, superimposed strata and residual rocks, which are common in ophiolite belts with residual oceanic crust, and are also important ductile shear deformation belts and blue amphibole metamorphic belts at low temperature and high pressure.
Small and medium-sized plates such as Tarim, China and Yangtze are dominant and micro-landmasses are developed, which is the most basic geological feature of Chinese mainland structure, which is significantly different from other continental structures in the world and controls the geological evolution since Phanerozoic.
I. Zone of stability
North China, Tarim, Yangtze and Cathaysian cratons constitute the stable core of China ancient plate. These cratons are small and active, and their growth, development and consolidation periods are different successively. The earliest continental crust appeared in the north of China and gradually spread to the south.
(1) North China Craton
The core part is the North China ancient plate, which has an ancient basement of about 3.8 billion years and is a stable land mass consolidated after the Lvliang movement. The northern boundary of the North China Plate is bounded by the deep fault in the northern margin of inner mongolian axis to Chifeng and Kaiyuan. The southern margin is bounded by the Qilian-Qinling deep fault in the northern margin, east to the Korean Peninsula and west to the Altun fault.
Within the North China Plate, Mesoproterozoic is characterized by transitional caprock. Shallow carbonate rocks dominated from Sinian to Middle Ordovician, rose to land after Middle Ordovician, invaded again in Middle Carboniferous, and turned into continental deposits in the late Early Permian, ending the history of transgression. In the early Indosinian period, Qinling Ocean and Qilian Ocean closed and collided with the Yangtze River. Since Jurassic, influenced by the Pacific plate, Yanshanian intrusive rocks and volcanic rocks have been widely developed in the eastern foot of Taihang Mountain. After Mesozoic, the North China Plate was divided into five secondary structural units with alternating uplift and depression by four northeast or northeast deep faults: Alashan Uplift, Shaanxi-Gansu-Ningxia Depression, Shanxi Uplift, Huabei Depression and Jiaoliao Uplift.
(2) Tarim Craton
The core of Tarim Craton is Tarim Basin. The northern boundary of the craton is the deep fault in the southern margin of Zhongtian Mountain, the southern boundary is the deep fault in the northern margin of Karakorum Mountain, and the eastern part is the Altun fault.
Within the craton, the Mesoproterozoic deposits are similar to those of the North China Craton, with active continental margin deposits only at the margin. The craton basement was finally reinforced after 850 million years. From the late Neoproterozoic to the early Late Paleozoic, marine sediments such as large carbonate rocks developed in the interior and margin of Tarim plate. After the late Permian, it gradually evolved into a large continental basin. Mesozoic and Cenozoic are mainly intermountain and piedmont depression deposits, with transgression in the west.
(3) Yangtze Craton and Cathaysian Block
The Yangtze Craton is bounded by the Yang Shan-Tongcheng fault in the north, the Shaoxing-Jiangshan fault in the southeast, the Longmenshan-Honghe fault in the west and the South Yellow Sea in the east. The Cathaysian land block has been cracked many times since the late Qingbaikou period, and the main part is located in the Cathaysian ancient land. The separated landmasses are scattered in the South China Sea islands such as Qiongnan and Xisha and the East China Sea. In Caledonian, the Yangtze Craton and Cathaysian Block jointly formed the South China Plate.
Thick Mesoproterozoic fold basement is widely distributed in the Yangtze Craton, and the main body was finally consolidated during the Jinning Movement. The stable marine sedimentary caprock began in Sinian and lasted until the early and middle Triassic. At the end of Caledonian, Cathaysian block combined with it to form South China Craton. Since the Middle-Late Triassic, except the upper Yangtze Sichuan Basin, other areas have been seriously reformed, and the deposition mainly occurred in newly formed continental lake basins such as foreland basin, pull-apart basin and extension basin.
Second, the activity area
The orogenic belt is mainly formed on the continental margin, develops around the landmass and is spliced between plates. Many microplates are often embedded in orogenic belts, and the combination of microplates also forms a combined belt. All these make the structure of orogenic belt very complicated. After plate collision, the plate joint area is repeatedly cracked and welded, which makes the early features re-form or overlap. Therefore, most of the four major orogenic systems in China are compound orogenic systems.
(1) Tianshan-Meng Xing orogenic system
It is composed of the Siberian plate and the continental margin orogenic belt of Tarim and North China plates, and is a Caledonian-Variscan composite orogenic system. At the eastern and western ends of the Siberian continental margin and the Tarim and North China continental margins, there are a large number of ancient microplate or block groups, as well as blocks separated from the North China and Tarim landmasses. In addition to Jiamusi-Songnen microplate, there is also Xilinhot landmass in the east, which may have been a continent with complex internal structure. There are Junggar, Yili microplate and Middle Tianshan Mountains in the west.
(2) Altun orogenic belt
Transition zone between Tarim plate and North China plate, Qilian plate and Qaidam plate. The belt experienced a strong strike-slip transformation and reduced overlap in the later period. There are two Paleozoic ophiolite belts in Qinghai, Lapeiquan and Mangya, and the central uplift belt of Jinyanshan, which is composed of metamorphic rocks of Mesoproterozoic and Lower Paleozoic, is located between the two ophiolite belts. Altun was probably a small ocean basin in the early Paleozoic, which was connected with the ocean basins of Qin, Qi and Kun, and closed the Caledonian movement.
(3) Central orogenic system
The central orogenic system is a composite orogenic system among the three ancient plates of Tarim, North China and Yangtze. The western segment of the Tarim, North China and Yangtze paleoplate junction zone is Kangxiwa fault, which is bounded by the deep fault in the northern margin of Qilian-Qinling Mountains. After crossing the Tan-Lu fault, it is considered to extend to the Kangxiwa-Shangnan-Muping line. In the south, it is bounded by the Yang Shan-Tongcheng fault and adjacent to the Yangtze Craton. The central orogenic system is a compound orogenic system that is opened and closed many times. It experienced continental collision in Jinning period, Caledonian period and Variscan period and strong intracontinental subduction orogeny in Indosinian-Yanshan period.
(4) Qinghai-Tibet orogenic system
It is a giant orogenic system between Yangtze plate and Gangdise-India plate. The northern part is bounded by the Bangongcuo-Nujiang suture zone, adjacent to the central orogenic system and the South China plate. On the south side of Bangongcuo-Nujiang belt are Gangdise microplate, Yarlung Zangbo microplate junction zone and Himalayan orogenic belt, which are connected with Indian landmass through Himalayan main boundary faults. The stability of this area is poor and the geological evolution process is complicated.
(5) South China orogenic system
Located between the southeast edge of the Yangtze River and the Huaxia edge. The main body of Caledonian in South China developed in the margin of Cathaysian continent and the Shaoyang-Chengbu line from the western boundary to the margin of Yangtze continent. Youjiang area on the Yangtze continental margin was basically consolidated in Jinning period, and the Devonian-Carboniferous and Early-Middle Triassic were NW-trending rifted and folded in Indosinian movement, belonging to Indosinian orogenic belt (Ren Jishun, 1997).
(6) Taiwan orogenic belt
It is a Mesozoic-Cenozoic orogenic belt, a part of the Japan-Philippines island arc orogenic belt on the continental margin of the Eurasian plate, and is connected with the Philippine Sea plate through the vertical valley junction of Taitung. The longitudinal valley of Taidong is a Neogene thrust plate combination zone formed on the basis of the subduction zone of Yuli ancient Pacific plate in Yanshan period.
(VII) Wandashan Fold System
Wandashan fold system is a part of the Schott Alin fold belt, and it is a continental margin accretion belt formed along the eastern margin of the Asian continent from late Jurassic to early Cretaceous. It is mainly composed of Carboniferous-Permian limestone and greenschist, Middle-Upper Triassic radiolarian siliceous rocks, turbidite, melange, and lower-middle Jurassic clastic rocks and volcanic rocks. Some of these strata appeared in the late Jurassic strata in the form of foreign rocks. The thrust nappe structure in this area is very complex, and granite emplacement occurred in Indosinian and Yanshan periods.