Miocene tectonic deformation and mineralization in the northern margin of Qinghai-Tibet Plateau and its adjacent areas

Xinjiang is characterized by "three mountains and two basins" (Figure 2-6- 1). Altai Mountain, Tianshan Mountain and Kunlun-Altun Mountain in the northern margin of Qinghai-Tibet Plateau constitute a magnificent mountain system in western China, showing obvious normal topography. At the same time, represented by Junggar basin and Tarim basin, it presents a negative landform with obvious subsidence. The existing research data show that this geomorphological structure model is the result of Cenozoic tectonic movement in Xinjiang.

Figure 2-6- 1 Central Asia landform and main fault distribution map

① Ili basin; ② Fergana Valley; (3)sil darling； ④Chuzaresu； ⑤ Kazkum

Generally speaking, except for the intermountain basin, the Cenozoic tectonic activities of the three mountain systems in Xinjiang are very strong, while the Cenozoic tectonic activities of the Tarim Basin and Junggar Basin in great basin are relatively weak (Figure 2-6-2). According to the analysis of metallogenic conditions of sandstone-type uranium deposits, Tarim basin and Junggar basin are favorable metallogenic areas for sandstone-type uranium deposits, and some intermountain basins in Tianshan Mountain, such as Yili basin, Tuha basin and Kumish basin, are the result of Cenozoic tectonic action.

Figure 2-6-2 Profile of SN- strike Geomorphological Structure in Xinjiang

This book mainly discusses and analyzes the Cenozoic tectonic movement and its control over sandstone-type uranium mineralization, emphasizing the Miocene tectonic deformation in the northern margin of the Qinghai-Tibet Plateau and its adjacent areas and its relationship with sandstone-type uranium mineralization; The characteristics of Cenozoic tectonic movement in southern Yili basin, Dingshan area in northern Junggar basin and Tarim basin and its control on sandstone-type uranium deposits are emphatically expounded.

The collision between India and the Asian continent, which started around 65Ma, and the subsequent continental convergence were the most important tectonic events in the Cenozoic Asian continent, which controlled the Cenozoic tectonic deformation in western China and even in the Asian continent. Stock and Molnar et al. (1988) calculated and analyzed the ancient latitudes of Indian continent in different periods of Cenozoic, and calculated the northward movement speed of Indian continent. According to the results of paleomagnetic survey, Chen et al. (1993) and Xiao Xuchang et al. (2000) calculated the positions of paleolatitudes such as Lhasa block and Qiangtang block, and then estimated the shortening of the crust. The results reveal the change of convergence rate between India and Asian continent in Cenozoic, indicating that the deformation of Qinghai-Tibet Plateau has staged characteristics.

Based on some geological data in the northern margin of the Qinghai-Tibet Plateau (Figure 2-6- 1), this book briefly reviews the tectonic deformation events that occurred in Miocene, and preliminarily discusses the influence of this tectonic event on the mineralization in western China.

I. Mountains in the southern part of the Qinghai-Tibet Plateau and its northern edge

The ocean drilling results of alluvial fans in the South China Sea (Yinggehai), the East China Sea of China and the Bay of Bengal show that the Cenozoic sedimentation rate suddenly accelerated in the early Miocene. According to the results of stable isotope tracing, the south-central Qinghai-Tibet Plateau experienced rapid uplift-detachment in the early Miocene (25 ~ 20ma). Apatite fission track dating results show that Altun-Kunlun Mountain in the northern margin of Qinghai-Tibet Plateau began to uplift and denude in Oligocene, and the uplift rate accelerated in the early Miocene. The magnetostratigraphic study of the Hongsanhan section in Qaidam Basin shows that the sedimentation rate accelerated from the late Oligocene to the early Miocene (28 ~ 26 Ma), suggesting that a major tectonic event occurred in the northern margin of the Qinghai-Tibet Plateau in the early Miocene. The sedimentary-tectonic deformation analysis of the basin, combined with the restoration of paleostructure and landform, reveals that the Altun fault zone had a fault location migration event during the late Oligocene-Miocene; According to the field investigation and indoor sedimentological statistical analysis, the grain size of Cenozoic sedimentary materials in the Qalesayi Basin in the northwest of Altun Mountain increased sharply in the early Miocene (25Ma), the proportion of conglomerate layer in the stratum increased obviously, and the composition of sandstone detrital materials changed suddenly, and the sedimentary facies and sedimentary environment changed suddenly, reflecting the changes of geomorphology and structural properties of the source area, indicating that the source area had undergone rapid uplift and stripping events. According to the δ 14C and δ 18O values of carbonate cements in Cenozoic sedimentary materials in Jianggalesayi basin, it is inferred that the climate in the northern margin of the plateau changed in the early Miocene (25 ~ 23 Ma), indicating that the plateau experienced rapid uplift.

Second, Tarim basin

At present, the Tarim basin is high in the west and low in the east. However, the recovery analysis of lithofacies palaeogeography shows (Figure 2-6-3 and Figure 2-6-4) that there were still marine strata in the southwest of Tarim during Oligocene, while the eastern part was mainly continental strata at that time, indicating that the terrain was high in the east and low in the west (Figure 2-6-3). With the convergence and closure of the Indo-Asian continent, the Pamirs structural knot was formed, and seawater withdrew from the basin westward from the late Oligocene, and no marine strata developed in the basin. In the southwest of Tarim Basin, piedmont molasses deposits appeared, and in Maingard sag and Kuche sag in the east of the basin, Miocene was lacustrine strata (Figure 2-6-4). The above analysis shows that the topography of Tarim basin has changed from high in the east and low in the west to high in the west and low in the east. This change began in the early Miocene and may not be completed until the end of Miocene.

Fig. 2-6-3 Oligocene Paleogeography Diagram of Tarim Basin

(Revised according to Xinjiang Paleogeographic Atlas)

1- semi-block-block platform facies belt; 2- coastal beach-bar facies belt; 3- tidal flat-lake facies belt; 4- piedmont accumulation facies; 5- fluvial facies; 6- salt lake facies; 7- fluvial facies; 8- coarse clastic deposition; 9- detrital deposition; 10- gypsum and mud deposition; 1 1- argillaceous deposit

Third, Tianshan Mountain.

The results of apatite fission track test by Hendrix et al. (1994) reveal that Tianshan Mountain (middle section) experienced rapid uplift and erosion in the early Miocene (25Ma). The apatite fission track test and simulation analysis in the west Tianshan and Bogda areas also revealed that the west Tianshan and the east Tianshan experienced rapid erosion in the early Miocene (25 ~ 24 Ma). Yili basin is an intermountain basin developed in Tianshan orogenic belt. Drilling and field investigation have confirmed that there are many unconformities between Mesozoic and Cenozoic strata in Yili basin, which represents the existence of multi-stage structural deformation events. Among them, the most important structure was the first tectonic activity in the early Miocene, which developed in the south and north of Yili Basin, and the Daladi section was the most typical, indicating that the Daladi syncline structure composed of Jurassic-Cretaceous was covered by Pliocene unconformity. In Dongmazha area of Yili basin, the Miocene unconformity directly covered the folded and deformed Permian volcanic rocks.

Figure 2-6-4 Miocene Sedimentary Facies of Tarim Basin

(Revised according to Xinjiang Paleogeographic Atlas)

Ⅰ—alluvial fan facies; Ⅱ1-braided river subfacies; Ⅱ 2-fluvial alluvial plain subfacies; Ⅲ —— Intermittent lacustrine facies

Fourthly, Junggar basin.

In the Dingshan area in the north of Junggar Basin, the Eocene-Oligocene Wulunguhe Formation is a river-alluvial fan sedimentary system under semi-humid and semi-arid climate conditions, while the Miocene Suosuoquan Formation is a sedimentary material under extremely dry and hot conditions in inland swamps and lakes. We estimated the C3-C4 ecosystem by using the δ 14C and δ 18O values of calcium nodules in rock strata, and found that C4 plant types in this area suddenly increased in the early Miocene, which also reflected the abrupt change of paleoclimate and paleoenvironment (Figure 2-6-5). The apatite fission track test results of granite in Genghis Khan Mountain, Sawuer Mountain in western Junggar and Karamay Mountain in eastern Junggar show that the denudation of mountains occurred in Cretaceous-Paleogene, but the apatite temperature-time inversion simulation analysis reveals the existence of early Miocene structural denudation events of mountains.

Verb (abbreviation for verb) Miocene volcanic activity

Quaternary volcanic activity in the Qinghai-Tibet Plateau and its northern margin is well developed. Tianshan orogenic belt is only controlled by Fergana fault zone in Tuoyun basin of western Tianshan Mountain, and volcanic activity is developed. In other areas of northern Xinjiang, Quaternary basalts erupted only in Qiaoxiahala and Qinghe in Altai, and the Ar-Ar dating result was (17.59 0.05) Ma. The test and analysis of rare earth and trace elements show that the basalt has the characteristics of continental overflow basalt. Volcanic activity may reflect the remote effect of early Miocene tectonic deformation events in the northern margin of Qinghai-Tibet Plateau, Tarim Basin and Tianshan Mountains.

Figure 2-6-5 Proportion Map of C4 Plant Types in Cenozoic Strata in Northern Junggar Basin

Six, Miocene mineralization

Quaternary mineralization in the south and southeast of Qinghai-Tibet Plateau is very important, and many important metallogenic belts have been discovered, such as Sanjiang metallogenic belt and Yarlung Zangbo metallogenic belt. In the northern margin of the plateau, due to the limitation of natural conditions, the research degree of Quaternary mineralization is seriously insufficient.

In Central Asia, the large-scale mineralization of sandstone-type uranium deposits mainly occurred in Cenozoic. In Chuzaresu, Sirdarin, Kazakhstan, and Kazkum, Uzbekistan, huge uranium-rich areas were formed in Cenozoic. Many in-situ leachable sandstone-type uranium deposits have also been discovered in the southern margin of Yili Basin and the southwestern margin of Turpan-Hami Basin, and the first in-situ leachable sandstone-type uranium mining base in China has been established in Kujiertai, the southern margin of Yili Basin. The existing dating data show that the metallogenic age of sandstone-type uranium in the southern margin of Yili basin mainly occurred after Miocene. The field geological survey shows that the tectonic deformation in the early Miocene played an important role in controlling the mineralization of sandstone-type uranium deposits in the southern margin of Yili Basin. The fold deformation in the early Miocene caused the target layer of mineralization (Jurassic coal-bearing strata) to tilt in the south of the basin, formed a stable slope zone in the south of the basin, and formed a perfect groundwater recharge and drainage system, which provided a structural environment for long-term large-scale mineralization. In addition, the U-Pb dating results of the ore show that an important uranium mineralization occurred in the southwest margin of Hami sag in Turpan-Hami basin in the early Miocene (28Ma).

Seven. abstract

In a word, the tectonic deformation occurred in the early Miocene is very common in the northern margin of the Qinghai-Tibet Plateau and its adjacent areas, and its power source should come from the collision and convergence of the southern Indian plate and the Asian continent, which is related to the change of convergence rate of the two continents; However, due to geographical differences, the time of tectonic events is also different, and the time of northward deformation becomes younger; The tectonic deformation in this period led to the first rapid uplift and denudation of the mountains in the northern margin of the Qinghai-Tibet Plateau, the first rapid denudation of the Tianshan Mountains, and the changes in the topography and geomorphology of the Tarim Basin, as well as the accompanying climate changes in the Tarim Basin and Junggar Basin, which promoted the formation of the prototype of the "three mountains and two basins" landscape structure pattern in Xinjiang. At the same time, the tectonic deformation in this period played a very significant role in controlling the mineralization of sandstone-type uranium deposits in western China, and Miocene also became the start time of large-scale mineralization of sandstone-type uranium deposits in Mesozoic and Cenozoic basins in Xinjiang, China.

refer to

Chen, Liu Jian, Zhiming Sun, et al. 2005. Cenozoic stripping history of Altun Mountain-sedimentary record of foreland basin. Geological bulletin, 24 (4): 8 ~ 14.

Chen, Wang Xiaofeng, etc. Fission track evidence of Cenozoic uplift in Altun Mountain. Journal of Earth Sciences, 22 (5): 4 13 ~ 4 18.

Han Chongchong, Li, Cai, et al. 2004. Characteristics of neotectonic movement in Yili basin and its relationship with uranium mineralization. Geology of Xinjiang, 22 (4): 378 ~ 38 1.

Liu Hanbin, Xia,, et al. 2004. U-Pb isotopic geological characteristics of sandstone-type uranium deposits in Turpan-Hami basin. Journal of Geology, 25 (2): 196 ~ 198.

Liu Jian, Chen, Zhang Hongxi et al. 2003. Discussion on uranium-forming ability of Mesozoic and Cenozoic strata in northwest margin of Junggar basin. Journal of Geomechanics, 9 (3): 24 1 ~ 245.

Peng Xiling. 1998. Manifestations and characteristics of neotectonic movement in Xinjiang. Journal of Chengdu University of Technology, 25 (2):169 ~181.

Wang, Li Tiande. Geochemical characteristics and tectonic environment of Cenozoic volcanic rocks in eastern Altai. Tectonics and Mineralogy, 25 (3): 282 ~ 289.

Wang Jun 1998. Uplift of Karibasheng and Kuzigan plutons in West Kunlun-Evidence from apatite fission track analysis. Geological Review, Volume 44, No.4: 435 ~ 442.

Zhiming Sun, Yang Zhenyu, Ge Xiaohong, et al. 2004. Research progress of Paleogene chronology in the northern margin of Qaidam basin. Geological bulletin, 23 (9 ~ 10): 899 ~ 902.

Xia, Hou Yanxian et al. 2002. Isotopic geological characteristics of sandstone-type uranium mineralization in Yili basin. Uranium Geology,18 (3):150 ~154.

Xiao Xuchang and Li Tingdong. 2000. Tectonic evolution and uplift mechanism of Qinghai-Tibet Plateau. Guangzhou: Guangdong Science and Technology Press.

Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region. Regional geology of Xinjiang Uygur Autonomous Region. Beijing: Geological Publishing House, 207 ~ 265.

Yin An. 200 1. Geological evolution of Himalayan-Qinghai-Tibet Plateau orogenic belt-growth of Phanerozoic Asian continent. Journal of Earth Sciences, 22 (3): 193 ~ 230.

Zhang Qianfeng, Hu Aiqin, Zhang Guoxin, et al. Isotopic age evidence of Mesozoic-Cenozoic magmatism in Altai area. Geochemistry, 23 (3): 269 ~ 280.

Chen Y, Cogne J.P, Courtillot V., Tapbonnier P. and Zhu X.Y Cretaceous paleomagnetic results in western Tibet and their tectonic significance. Journal of Geophysical Research, 98 (B10):17981~17999.

Chen, Yin An, Chen Bailin. 2004. Sedimentary records of Cenozoic left-lateral strike-slip movement in the middle segment of Altun fault zone. International geological review, 46:839~856

Chen, Wang Xiaofeng, Feng Xiaohong, et al ... 2002. New evidence of stable isotopes for the uplift of mountains in the northern margin of Qinghai-Tibet Plateau. China Science (B), 32 (Supplement): 1~ 10

Clift P., Lin J. and Barckhausen U.2002. Evidence of continental crust with low bending stiffness and low viscosity during continental cracking in the South China Sea. Marine and petroleum geology, 19:95 1~970

Hendrix M.S, Dumitru T.A and Graham S.A. 1994. Late Oligocene-Early Miocene Topping of Tianshan Mountains in China: Early Effect of Indo-Asian Collision. Geology, vol. 22, pp. 487-490.

Shares J. and Molnar P. 1988. The uncertainty and significance of the position of North America relative to the Faralon, Kula and Pacific plates in the Late Cretaceous and Tertiary. Geotectonics, 7: 1339~ 1384

(Chen, Gong Hongliang, Li Li)