Tarim plate is adjacent to Kazakhstan plate in the north (figure 1-2). China's Ili Block (part of microcontinent, Kochittaf, Ili), the Middle Tianshan Mountains, Tuha and junggar block are all part of the Kazakhstan Plate (Figure 12). The dividing line between Tarim plate and Kazakstan plate is generally located in the northern margin of South Tianshan Mountain, that is, along the northern slope of the Hake Mountain-Barentai-Kumish-Cabala Line (Zhang Guangya,1994a; Liu et al.,1994; Chen Fajing et al.,1996; Li Xiangdong and Li Maosong,1996; Jia Chengzao, 1997). On the north side of the line are Ili block and Middle Tianshan block, and on the south side are the northern margin of Tarim plate and Kuruktag fault uplift. It is generally believed that this line extends westward and is connected with the nikolayev line, but Che Che Cheng (1994), Li Xiangdong and Li Maosong (1996) think that this line extends westward into the territory of the former Soviet Union and is connected with the fault zone on the southern edge of the Nalun block, and the nikolayev line (Karatau-Telskoy fault zone) extends into the territory of China, which is equivalent to the northern boundary of the Middle Tianshan Mountains in a narrow sense, namely.
Tarim plate and Paleozoic orogenic belt in Central Asia, north of China-Korea plate and south of Siberia plate, are typical zones where continental lithospheric plates and blocks (or terranes) diverge, converge and collide, belonging to the Central Asian tectonic domain, which Xiao Xuchang and others (199 1) call the ancient Central Asian composite giant suture zone. The Central Asian tectonic domain north of Tarim plate and Xinjiang include a series of blocks belonging to Tarim plate, Kazakhstan plate and Siberia plate (Figure 1-2). These blocks can be divided into continental crust, oceanic crust, island arc and composite blocks (Coleman, 1989).
Yili-Middle Tianshan massif is continental crust, and the basement of Mesoproterozoic-Neoproterozoic medium-deep metamorphic rock series is developed. The age values of these basement rocks are: 600 ~ 1500ma (Checheng, etc.,1994); 1306Ma 200Ma and1397ma18ma (Li Xiangdong and Li Maosong,1996); 1420Ma, 157 1Ma, 1730Ma (how, 1994, 1995). In addition, Neoarchean granite gneiss and Proterozoic metamorphic low amphibolite (how, 1995) are also seen in Barentai and Xingxingxia. Aeromagnetic data show that there is a strong magnetic ancient basement under the Yili block, which may be Archean (Chechengdeng, 1994). The development of moraine layer in Sinian caprock in Yili block shows that it was once a part of Xinjiang ancient craton assembled at the end of Neoproterozoic.
Figure 1- 1 Schematic diagram of the distribution of plates and blocks (terranes) in the Asian continent from Siberia plate to India plate.
(According to Ma Xingyuan,1987; Coleman, 1989 simplified)
Tectonic unit: ID- Indian plate; J- junggar block; K- Kazakhstan plate; Peak pulse in Pamirs; Sib-Siberian plate; Ta- Tarim plate; Heaven-Tianshan Mountain.
Black thick lines represent strike-slip faults and solid sawtooth lines represent thrust faults.
The island arc block in North Tianshan Mountain is composed of east-west calc-alkaline complex, which is a volcanic arc developed along the southern margin of junggar block.
Tuha and junggar block belong to composite blocks. There is a strong magnetic crystalline basement (Ma Ruishi et al., 1993) in Tuha block, which is a Devonian-Carboniferous thick island arc calc-alkaline volcanic rock. The caprock in junggar block is thick late Paleozoic (including Silurian) caprock deposit and Mesozoic-Cenozoic continental molasses deposit, and its basement properties are still controversial. Xiao Xuchang and others (1990) think that there may be no pre-Sinian crystalline basement in junggar block, which is mainly composed of oceanic crust. Zhang (1994) and He (1995) believe that the basement of Junggar basin should be Precambrian continental crust according to the characteristics of geological and geophysical gravity and magnetic fields.
The boundary between Kazakhstan plate and Siberia plate, which is composed of Yili-Middle Tianshan block, Turpan-Hami block and junggar block, is located in the Kelameili-Takzale suture zone. There are early Paleozoic and late Paleozoic island arc blocks in the southern margin of the Siberian plate (Figure 1-2). It can be seen from the above that in the Central Asian tectonic domain between Tarim plate and Siberia plate, the structural framework is characterized by the mosaic of blocks (terranes) and folded orogenic belts in different periods.
Figure 1-2 Plate tectonic zoning map of Tarim Basin and its adjacent areas (modified according to Jia Chengzao, 1997)
I- Tarim plate: I 1- northern margin of Tarim plate. Ⅰ 2-Tarim Plate:-Tarim Central Block; -Beishan Paleozoic rift; -Kuruktag fault uplift; -Altun fault uplift; -Iron Crick is broken; -Southwest Tarim foreland thrust belt; -Keping Duanlong. I3- southern margin of Tarim plate:-Paleozoic island arc of West Kunlun; -Freshwater bodies and foreland thrust belts
Ⅱ-Kazakhstan Plate: Ⅱ1-Early Paleozoic island arc and basement in the Middle Tianshan Mountains; Ⅱ 2-Ili Block (Ili-Cockchitev microcontinent); Ⅱ 3—Late Paleozoic island arc in North Tianshan; I4- junggar block; Ⅱ 5-tu-ha block; Ⅱ 6-SIL River Block
Ⅲ-Siberian plate: Ⅲ1-Late Paleozoic island arc in the southern margin of Siberia; Ⅲ 2 —— Early Paleozoic island arc in the southern margin of Siberia
Ⅳ-Qaidam block (or plate): Ⅳ1-Qaidam block; Ⅳ 2-North Qilian Block (or accretionary wedge); Ⅳ 3—Middle Qilian Block (island arc); Ⅳ 4-South Qilian block (or back-arc basin); Ⅳ 5-Qimantage accretionary complex; V- Tethys; V 1- Qiangtang block; V2- Lhasa Block
The southwest boundary of Tarim plate is Kangxiwa suture zone, and the southeast boundary is Altun fault zone (how,1995; Chen Fajing et al.,1996; Jia Chengzao, 1997) (Figure 1-2). The south of Tarim plate to India plate is a collage formed by a series of block collisions and accretion, belonging to Tethyan tectonic domain. This tectonic domain evolved with pre-Tethys Ocean (Zhongdalai and Ding Lin, 1993), Paleo-Tethys Ocean and Neo-Tethys Ocean, and experienced a complex discrete convergence process.
The Tethys tectonic domain south of Tarim plate mainly includes a series of small blocks such as Qaidam, Qiangtang, Lhasa (Gangdise) and Songpan-Ganzi (Figure 1-3, Ma Wenpu,1992; Wang Chengshan and Zhang Shaonan, 1996). The middle Jinning period of Qaidam massif is a Neoproterozoic folded basement, and the stable carbonate caprock of Sinian-Early Paleozoic was folded and metamorphic in the late Early Paleozoic, uplifted in the late Paleozoic, and developed in Mesozoic-Cenozoic basins. Songpan-Ganzi block is dominated by middle-upper Triassic shallow metamorphic rock series, and some are older metamorphic rock series and micro-landmasses. The Qiangtang Block in the Early Permian is composed of the South Qiangtang Block from Gondwana Mainland and the North Qiangtang-Changdu Block from South China Mainland, in which the Changdu Block has pre-Sinian and early Paleozoic metamorphic basement, and the oldest stratum in the South Qiangtang Block is pre-Devonian (Wu Yinglin et al., 1996). Lhasa block was split from Gondwana mainland, and the pre-Sinian basement was mainly exposed in Nyainqentanglha Mountain.
Figure 1-3 Tethys suture zone distribution map
(According to Ma Wenpu, 1992, modified)
1- Guterres suture area; 2- New Tethys suture zone; 3- Fault.
I —— the southern edge of East Kunlun; Ⅱ—Jinsha River; Ⅲ —— Ganzi —— Litang; Ⅳ —— Ailao Mountain; V- Changning-Menglian; ⅵ —— Bangong Lake —— Dong Qiao —— Ding Qing; ⅶ-Yarlung Zangbo River.
Bs- Baoshan plot; Id- India plate; LC- Lincang block; Ls- Lhasa block; Qd- Qaidam block; Qt- Qiangtang block; TL- Tarim plate; Yz- Yangtze plate
The Tarim plate system bounded by the suture zone on the northern margin of the southern Tianshan Mountains, the Kangxiwa suture zone and the Altun fault zone has been cracked from the Xinjiang ancient craton (or Proterozoic Xinjiang plate and Xinjiang ancient continental plate) since Sinian (Huang et al.,1990; Xiao Xuchang et al., 1990,1991; Tang Yaoqing et al.,1993; Zhang,1994; How, 1995). Xinjiang ancient craton was developed on the basis of Archean continental core in Tarim. Archean rocks are large-area gray gneiss at the end of East Tianshan Mountain and bimodal volcanic rocks with granulite facies on the northern slope of Altun Mountain, belonging to greenstone series. The Kulukatatobrak area in Glakele is a clastic supracrustal rock, containing a small amount of gray gneiss and metamorphic basic lava (higher,1993; How, 1995). The oldest isotopic age of these gneiss is 2580～3263ma (Zhang, 1994). After the Tsinger movement in the late Neoarchean and the land movement in the late Proterozoic, the Tarim ancient land has been extended to the Middle Tianshan-North Tianshan-Junggar-Altai and Tiekelike area in southwest Tarim. From Mesoproterozoic to Neoproterozoic, Tarim ancient land split into Proterozoic Guttari Wood Plate and Proterozoic Junggar Plate, which were separated by Proterozoic South Tianshan Ocean, occupying the present South Tianshan Mountains and the northern margin of Tarim Basin (Figure 1-4A). South of Proterozoic Limu Plate are Proterozoic Kunlun Ocean and Proterozoic Qiangtang Plate. After the Tarim Movement at the end of Neoproterozoic (the end of pre-Sinian), the wood plate of Yuan Guttari combined with the plate of Proterozoic Junggar and the plate of Proterozoic Qiangtang to form the Xinjiang ancient craton, which was separated from the Siberian ancient plate by the Proterozoic Asian Ocean to the north (Huang et al., 1990) (Figure 1-4B). The Sinian system in Altai, northern Xinjiang is a continental slope deposit, without moraine layer, and the Cambrian system does not contain phosphorus. However, the Sinian system of Kazakhstan, Tarim and South China plates all belong to platform deposits, containing moraine layers, and the Lower Cambrian has phosphorus-bearing formations, indicating that there was an ancient craton in Xinjiang at the end of the pre-Sinian period, which was a part of Gondwana supercontinent and far away from the Siberian ancient plate.
Fig. l-4 Schematic diagram of plate activity in Middle and Late Proterozoic in Xinjiang and its adjacent areas.
(According to Huang et al., 1990)