In the Early Paleozoic Cambrian, except for the ocean basin in the northern Tangbale area, this area is still in a stable period, mainly in the coastal and shallow sea environment, with phosphorus-containing clastic rocks and biolimestone deposits (Figure 1- 15a). The Ordovician entered the formation and development period of the ancient Asian Ocean (Figure 1- 15b, c, d). The early Ordovician crust in the northern margin of Yili basin gradually stretched, and the middle Ordovician Polokolo area formed a passive continental margin of magma. Wang Baoyu et al. (1997) once thought that the Ordovician in this zone was an early Polokolo rift basin, and there was no ocean basin, while Xiao Xuchang et al. (2005) thought that this zone was a combination of Junggar-Balkhash microfacies plate and Muyunkum-Korcyl Ku- Yili microfacies plate in Harbin-Junggar plate. According to our comprehensive study of various geological characteristics of the fault system in this belt, it is indicated that there are oceanic crust ultramafic rocks (lherzolite from Gendaban and Harkjerr) and volcanic rocks in this belt from the Ordovician extensional passive continental margin to the Silurian active continental margin slope facies, which proves that this belt is connected with Chu-Ili in the west and Tao Tao-Silurian ocean area in Kenda in the Ordovician-Silurian, and with Gangou-Kangurta in the east. The Ili Ocean in this area finally closed in the Late Silurian (Figure 1- 15e).

The formation of the southern Tianshan ocean area was slightly later than that of the Ili ocean area. In the early Ordovician, due to the tensile stress of the Ili Ocean about to open, the non-orogenic "A" type potash granite intrusion appeared in the western section of Nalati Mountain (Figure 1- 15b). In the Middle Ordovician, the Proterozoic suture zone in the southern margin of Nalati Mountain was stretched again, accompanied by the second intrusion of "A" type potash granite in Ladun Daban area (figure 1- 15c). The late Ordovician was the formation period of ocean basin, which gradually opened from north to south on the extension belt of the southern margin of Nalati Mountain. In the Early Silurian, the southern Tianshan Ocean began to subduct northward with the Wusun-Awulale microplate, forming a local extensional environment in the Jingbulake area on the north side of the Nalati ancient continental margin (Figure 1- 15e), and the basic-ultrabasic rocks of copper-nickel ore emplaced in the form of diapir (Zhang Zuoheng et al., 2007).

Seen from the ophiolite melange belt exposed in the east neighborhood of this area, from north to south, it is Guluogou-Wuwamen, Yushugou-Tonghuashan, Huolashan-Kule and Heiyingshan-Mandalek-Seyakelak ophiolite melange belt, etc. It is worth noting that a set of non-ophiolite-type basic-ultrabasic rock complexes are intermittently exposed along the fault along the Guluogou-Wuwamen-Baoertu-Gongbaizi line in the southern margin of Nalati Mountain, and the intrusion age is Precambrian and Paleozoic (Jiang Changyi et al., 2000). Therefore, the deep fault zone, as an important dividing line between the middle Tianshan Mountains and the south Tianshan Mountains, was once an ultra-long active zone. Dong Yunpeng et al. (2005) studied the tectonic environment of the formation of the Uwamen ophiolite, and proposed to connect the Yushugou ophiolite belt with the Uwamen-GongBai Zi structural belt. This view is debatable, because a large number of SILURIAN island arc volcanic rocks, clastic rocks and marble are exposed in the southern margin fault zone of Yongshugou ophiolite melange belt, and are invaded by Devonian granite, including amphibole schist structural blocks. It is inferred that this belt is also an early Paleozoic structure. Therefore, according to the spatial structure model, the Yushugou ophiolite melange belt should be an independent ophiolite belt. We think that this belt may be concealed in the structural belt on the northern slope of the Hake Mountain in the west, and then it may be connected with the subduction-overlap belt superimposed in the early and late Paleozoic on the southern margin of the adjacent Jiyinzhiketao Mountain (how, 2000,2001), which needs further study. Kule ophiolite is the southernmost tip of ophiolite belt. Long et al. (2006) determined its formation age as Middle Silurian (425±8Ma) by SHRIMP zircon U-Pb dating, which changed the understanding that ophiolite belt was formed in Devonian (et al., 1996). In addition, Feng Xinchang et al. (2005) and Cai Dongsheng et al. (1996) discovered the unconformity of Yeyungou Formation of Lower Carboniferous on ophiolite, which confirmed that the Carboniferous wei county Formation was unconformity with the underlying strata found in the seismic profile study of northern Tarim and Tazhong, and the Kule Narrow Ocean Basin experienced Silurian. Whether this belt can be connected with the Balagon ophiolite in the Kuokesayan Mountains in the southwest (Wang Chao et al., 2007) deserves attention.

Comprehensive analysis shows that the evolution of the southern Tianshan ocean basin has a trend of gradual change from north to south. This means that the Precambrian basement in the northern margin of Tarim ancient land continued to split and proliferate from north to south from late Ordovician to late Silurian, and separated from Tarim ancient land, forming three broadband underwater island chains with carbonate platform nature sandwiched between troughs (Figure 1- 15d, e, f), in which the slopes at the junction of island chains, troughs and ocean areas contain argillaceous rocks and carbonate rocks.

The southern Tianshan ocean tectonic framework, which is the same as the island chain, experienced complex tectonic thermal events and deformation reentry mechanisms during its formation and extinction. According to the 40Ar-39Ar plateau age of Changawuzi ophiolite pyroxene, the ocean basin in the southern margin of Nalati in the southern Tianshan Mountains is 439Ma (Hao Jie et al., 1993), which represents the formation age of ophiolite in this belt. On the northern slope of Mount Hake in the same tectonic belt, the 40Ar-39Ar plateau age of Tekes blueschist is 415.37 2.17ma (Jun Gao et al., 1994), and the metamorphic age of beryl blueschist facies is 4 15 ~ 408ma (0. According to the research of Dong Yunpeng et al. (2005), the Yushugou ophiolite belt was formed in the Late Ordovician (44018 ~ 439 Ma), in which the high-pressure granulite metamorphic ophiolite terrane can be regarded as a special terrane exposed on the present surface after the oceanic lithosphere dived to a depth of 40 ~ 50 km (its SHRIMP zircon U-Pb age is 392±7Ma). Therefore, the northward subduction of the ocean basin in this area should occur in the Middle Silurian (Figure1-Kloc-0/5e), and the collision occurred in the late Devonian, and the late Carboniferous entered the stage of intracontinental orogeny after collision.

2. Late Paleozoic (extinction of ancient Asian oceans)

The western Tianshan area entered a new tectonic evolution period from Devonian. In the Polokolo area, Devonian changed to the stage of compressional uplift and orogeny after the closure of Ili Ocean, and at the same time, the thrust nappe structure from south to north occurred, with granite emplacement. As a result, the plate movement of the ancient Asian Ocean entered the early collision orogeny stage. The southern Tianshan area is still a sedimentary area, and the Huolashan-Kule micro-ocean basin has been closed. According to the Devonian-Early Carboniferous radiolarian fossils found in siliceous rocks in the Heiyingshan-Mandalek ophiolitic melange belt in the southern margin (Shu et al., 2007; Wei Li et al., 2007), which is a narrow ocean basin in the Late Devonian, and other areas are still in the environment of carbonate platforms and troughs (Figure 1- 15g, h). The middle and late Devonian Boluokolo area entered the post-orogenic relaxation stage, and Bayingou area was the deepest rift, which laid the foundation for the Bayingou rift ocean basin in the northern Tianshan Mountains in the early Carboniferous (figure 1- 15h).

The Ebinur Lake-Bayingou area was pulled into the ocean in the early Carboniferous, and the passive continental margin in the southern margin of the ocean area was Bizhentao-Hanjiga shallow carbonate basin. A series of extensional faulted volcanic sedimentary basins have been formed in Yili basin, and the famous Axi gold deposit is located in the northern margin of the back-arc Tulasu faulted volcanic basin. According to the analysis of field structure and volcanic rock composition characteristics, the formation of Axi gold deposit is related to the upwelling deposition of gold-bearing hydrothermal solution along the edge of volcanic mechanism after volcanic activity ended. In the early Middle Carboniferous, Bayin Gully Ocean experienced two-way subduction, and a typical gully-arc basin system developed in its southern margin. Through field profile analysis (see Figure 1-8), the structural framework in this area can be divided into: ① Bayingou-Reed Gully-subducted ophiolite complex belt from north to south; (2) the volcanic arc on the ocean margin of Kuitun River; ③ Sanchahe pre-arc basin; (4) Dabate Island Arc; ⑤ Tulasu back arc faulted volcanic basin. The above Middle Carboniferous Dabate Island Arc evolved on the shallow-sea carbonate platform at the passive continental margin of the Early Carboniferous (Figure 1- 15i, j). The mineralization in this period includes chromite mineralization in ultramafic accumulation complex in ophiolite, small porphyry copper-molybdenum deposit in Dabate island arc and Lamasu porphyry-skarn medium-sized copper deposit in the same structural belt. In the late Middle Carboniferous, the northern Tianshan (Bayingou) micro-ocean basin subducted and reduced, forming a residual trough sedimentary environment with turbidity current sedimentary characteristics. The Middle Carboniferous in Yili Basin is in a dynamic environment of alternating opening and closing, with tension as the main factor and strong depression, forming a rift-type volcanic sedimentary basin. The shallow carbonate basin with the characteristics of residual sea in the southern Tianshan Mountains shrank continuously from the early Carboniferous to the middle Carboniferous, and finally disappeared in the late Carboniferous (figure 1- 15i, j, k). In the Late Carboniferous, this area experienced the late continental collision orogeny, with the southern Tianshan Mountains uplifted and uplifted, and the large-scale intrusion of granite basement in the northern and middle Tianshan Mountains was located in the structural uplift area, and the corresponding low-lying areas were filled with coarse debris of moralite facies (figure 1- 15l). At this time, the ore-bearing magma activity is very active, and the volcanic hydrothermal sedimentary xinyuan county-style Butai iron deposit occurs in siliceous rocks in Yili Rift Zone. After the last land-land collision in the Late Carboniferous, there was a strong exchange and upwelling of crust and mantle materials in the deep crust. In the Early Permian, Yili Basin, Alatao Mountain and Hanjishan collapsed into rift basins due to the overflow of upwelling magma (figure 1- 15m). At the end of Early Permian, the Ili Rift Zone was reopened after a brief closure, but the volcanic activity gradually weakened. The phenomenon of copper mineralization in the Permian Yili Rift Zone is very obvious, among which there are small copper deposits such as Kesbulak, Qunjisayi, Kezileke in southern Tibet and Qiongbulak in Awulala Mountain, all of which are closely related to the hydrothermal activity of the last volcanic magma intrusion in the early Permian.